C primer plus 6 编程练习答案

环境：vs2017

 /**编程练习2**/
 /**/
 #include<stdio.h>
 int main(void)
 {
     printf("张三\n");
     printf("张\n三\n");
     printf("张");
     printf("三\n");
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     printf("姓名：张三\n地址：中国\n");
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int    age = , days = ;
     printf("请输入您的年龄：");
     scanf_s("%d", &age);
     days = age * ;
     printf("您的年龄为：%d\n您的年龄转换成天数为：%d\n", age, days);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 void jolly(void);
 void deny(void);
 int main(void)
 {
     jolly();
     jolly();
     jolly();
     deny();
     getchar();
     return ;
 }
 void jolly(void)
 {
     printf("For he's a jolly good fellow!\n");
 }
 void deny(void)
 {
     printf("Which nobagy can deny!\n");
 }
 /**/
 #include<stdio.h>
 void br(void);
 void ic(void);
 int main(void)
 {
     br();
     ic();
     printf("India,China,\n");
     printf("Brazil,Russia\n");
     getchar();
     return ;
 }
 void br(void)
 {
     printf("Brazil,Russia,");
 }
 void ic(void)
 {
     printf("India,China\n");
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int toes = ;
     printf("toes为：%d\ntoes的2倍为：%d\ntoes的平方为：%d\n", toes,  * toes, toes*toes);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 void smile(void);
 int main(void)
 {
     smile();
     smile();
     smile();
     printf("\n");
     smile();
     smile();
     printf("\n");
     smile();
     printf("\n");
     getchar();
     return ;
 }
 void smile(void)
 {
     printf("Smile!");
 }
 /**/
 #include<stdio.h>
 void one_three(void);
 void two(void);
 int main(void)
 {
     printf("starting now:\n");
     one_three();
     printf("done!\n");
     getchar();
     return ;
 }
 void one_three(void)
 {
     printf("one\n");
     two();
     printf("three\n");
 }
 void two(void)
 {
     printf("two\n");
 }

 /**编程练习3**/
 /**/
 #include<stdio.h>
 int main(void)
 {
     int    a;
     float b,c;
     a = ;//整数上溢
     b = 3.4E38 + 10.0f;//浮点数上溢
     c = 0.1234E-10 / ;//浮点数下溢
     printf("%d\n%f\n%f\n",a, b, c);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int a = ;
     printf("请输入一个0-127中的一个整数：");
     scanf_s("%d", &a);
     printf("该数对应的ASCLL码为：%c\n", a);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     printf("\a");//警报
     printf("Startled by the sudden sound,Sally shouted,\n");
     printf("\"By the Grate Pumpkin,what was that!\"");
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     float a;
     printf("输入一个小数：");
     scanf_s("%f", &a);
     printf("%f\n%e\n%.2a\n", a, a, a);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int age = ;
     long min = ;
     printf("请输入您的年龄：");
     scanf_s("%ld", &age);
     min = age * 3.156E7;
     printf("转换为秒为：%ld秒\n", min);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int    main(void)
 {
     double a,c;
     int b;
     printf("请输入水的夸脱数：");
     scanf_s("%d", &b);
     a =  * 3.0E-23;
     c = a * b;
     printf("水分子数量为：%e\n", c);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main()
 {
     float tall_m, tall_cm;
     printf("请输入您的身高：");
     scanf_s("%f", &tall_m);
     tall_cm = 2.54*tall_m;
     printf("%.2f英寸转化为厘米为：%f厘米",tall_m, tall_cm);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main()
 {
     float cup,p,a,t,c;
     printf("请输入杯数：");
     scanf_s("%f", &cup);
     p = cup/;
     a =  * cup;
     t =  * a;
     c =  * t;
     printf("%f杯等于%f品脱，%f杯等于%f盎司，%f盎司等于%f大汤勺，%f大汤勺等于%f茶勺\n", cup, p, cup, a, a, t, t, c);
     getchar();
     getchar();
     return ;
 }

 /**编程练习4**/
 /**/
 #include<stdio.h>
 int main(void)
 {
     char surname[] ;
     char  name[];
     printf("请输入您的名：\n");
     scanf_s("%s",name,);////////////////////////////////注意！！！scanf_s()在输入数组时需要指明字段大小/////////////////////////////////////////
     printf("请输入您的姓：\n");
     scanf_s("%s",surname,);
     printf("您的名为：%s\n姓为：%s\n", name, surname);
     getchar();
     getchar();
     //getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<string.h>
 int main(void)
 {
     char name[];
     printf("请输入名字：\n");
     scanf_s("%s", name, );
     printf("\"%20s\"\n", name);
     printf("\"%-20s\"\n", name);
     printf("\"%*s\"\n", strlen(name) + , name);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     float a;
     printf("输入一个小数：21.29\n");
     scanf_s("%f", &a);
     printf("输入的数是：%.1f或%.1e\n", a,a);
     printf("输入的数是：%2.2f或%.3E\n", a, a);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     float heigh;
     char name[];
     printf("请输入你的姓名：\n");
     scanf_s("%s", name, );
     printf("请输入你的身高（米）：\n");
     scanf_s("%f", &heigh);
     printf("%s,你有%.3f米高", name,heigh);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(xoid)
 {
     float speed, size, time;
     printf("请输入以兆位每秒（Mb/s）为单位的下载速度和以兆（MB）为单位的文件大小\n");
     scanf_s("%f %f", &speed,&size);
     time =  * size / speed;
     printf("At %.2f megabits per second,a file of %.2f megabytes\n\
  downloads in %.2f seconds.\n",speed,size,time);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<string.h>
 int main(void)
 {
     char surname[];
     char name[];
     int length1,length2;
     printf("输入姓：\n");
     scanf_s("%s", surname, );
     printf("输入名：\n");
     scanf_s("%s", name, );
     length1 = strlen(surname);
     length2 = strlen(name);
     printf("%s %s\n", surname, name);
     printf("%*d %*d\n", length1, length1,length2,length2);
     printf("%s %s\n", surname, name);
     printf("%-*d %-*d\n", length1, length1, length2, length2);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<float.h>
 int main(void)
 {
     double a=1.0 / 3.0;
     float b=1.0 / 3.0;
     printf("a=%.6f\tb=%.6f\n", a, b);
     printf("a=%.12f\tb=%.12f\n", a, b);
     printf("a=%.16f\tb=%.16f\n", a, b);
     printf("float类型的最小有效数字为：%d\tdouble类型的最小有效数字为：%d\n", FLT_DIG, DBL_DIG);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define GALLON 3.785 //1加仑等于3.785升
 #define MILE 1.609   //1英里等于1.609千米
 int main(void)
 {
     float gallon, mile;
     printf("输入旅行里程：\n");
     scanf_s("%f", &mile);
     printf("输入消耗汽油量：\n");
     scanf_s("%f", &gallon);
     printf("油耗为：%.1f英里/加仑\n", mile / gallon);
     printf("油耗转换为：%.1f升/100公里\n", gallon*GALLON / (mile*MILE) * );
     getchar();
     getchar();
     return ;
 }

 /****编程练习5****/
 /**/
 #include<stdio.h>
 int main(void)
 {
     const int m_to_h = ;
     int m,h,left;
     printf("输入一个时间（分钟）：\n");
     scanf_s("%d", &m);
     while (m>)
     {
         h = m/m_to_h;
         left=m%m_to_h;
         printf("%d分钟转化为小时为：%d小时%d分钟\n", m, h,left);
         scanf_s("%d", &m);
     }
     getchar();
     //getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int a,b;
     printf("请输入一个整数：\n");
     scanf_s("%d", &a);
     b = a + ;
     while (a<=b)
     {
         printf("打印比该数大10的整数为:%d\n", a);
         a++;
     }
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     const int day_to_week = ;
     int days,week,left;
     printf("请输入天数：\n");
     scanf_s("%d", &days);
     while (days>)
     {
         week = days/day_to_week;
         left = days%day_to_week;
         printf("%d天转化为%d周%d天\n", days, week, left);
         scanf_s("%d", &days);
     }
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define FEET_TO_CM 30.48
 #define INCHE_TO_CM 2.54
 int main(void)
 {
     float heigh,inches;//inches英寸
     int foot;//英尺
     printf("输入身高(cm)：\n");
     scanf_s("%f", &heigh);
     while (heigh>)
     {
         foot = heigh / FEET_TO_CM;
         inches = (heigh - foot * FEET_TO_CM) / INCHE_TO_CM;
         printf("%.2fcm=%d英尺%.2f英寸", heigh, foot, inches);
         scanf_s("%f", &heigh);
     }
     getchar();
     //getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int sum=, count=,day=;
     printf("输入天数：\n");
     scanf_s("%d", &day);
     while (count++<day)
     {
         sum = sum + count;
     }
     printf("%d天挣了%d元钱\n", day, sum);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int sum = , count = , day = ;
     printf("输入天数：\n");
     scanf_s("%d", &day);
     while (count++ < day)
     {
         sum = sum + count*count;
     }
     printf("%d天挣了%d元钱\n", day, sum);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 void value3(double a);
 int main(void)
 {
     double a;
     printf("输入一个小数：\n");
     scanf_s("%lf", &a);
     value3(a);
     getchar();
     getchar();
     return ;
 }
 void value3(double a)
 {
     double b;
     b = a * a*a;
     printf("%lf立方为：%lf\n", a, b);
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int a, b;
     printf("\t*****求模运算*****\t\n");
     printf("输入一个数作为第2个运算对象：\n");
     scanf_s("%d", &a);
     printf("输入第二个数作为第1个运算对象：\n");
     scanf_s("%d", &b);
     printf("求模运算%d%%%d=%d\n", b, a, b%a);
     printf("输入下一个数作为第1个运算对象：\n");
     scanf_s("%d", &b);
     while (b>)
     {
         printf("求模运算%d%%%d=%d\n", b, a, b%a);
         printf("输入下一个数作为第1个运算对象：\n");
         scanf_s("%d", &b);
     }
     printf("结束\n");
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 void Temperatures(double h_tem);
 int main(void)
 {
     double h_tem;//华氏度
     printf("请输入华氏温度(输入非数字以退出)：\n");
     while (scanf_s("%lf", &h_tem)==)
     {
         Temperatures(h_tem);
         printf("请输入华氏温度(输入非数字以退出)：\n");
     }
     printf("程序退出\n");
     getchar();
     getchar();
     return ;
 }
 void Temperatures(double h_tem)
 {
     double s_tem;//摄氏度
     double k_tem;//开氏度
     const double h_to_s = 32.0;//华氏度转摄氏度要用到的常量值
     const double s_to_k = 273.16;//摄氏度转开氏度要用到的常量值
     s_tem = 5.0 / 9.0 * (h_tem - h_to_s);
     k_tem = s_tem + s_to_k;
     printf("%.2lf华氏度等于%.2lf摄氏度和%.2lf开氏度\n", h_tem, s_tem, k_tem);
 }

 /****编程练习6****/
 /**/
 #include<stdio.h>
 #define size 26
 int main(void)
 {
     char ch[size];
     int a;
     for (a = ; a<size; a++)
         ch[a] = 'a' + a;
     for (a = ;a < size;a++)
         printf("%c", ch[a]);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int row, clo;
     char ch = '$';
     for (row=;  row< ; row++)
     {
         for (clo = ; clo < row + ; clo++)
             printf("%c",ch);
         printf("\n");
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch = 'F';
     char start, end;
     for (end=ch;end>='A'; end--)
     {
         for (start=ch;start>=end;start--)
             printf("%c", start);
         printf("\n");
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     const char end = 'U';
     char start;
     int row, clo;
     for (row=,start = 'A'; start<=end;row++ )
     {
         for (clo = ;clo <= row;clo++)
         {
             printf("%c", start);
             start++;
         }
         printf("\n");
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     char start = 'A';
     char end;
     char ch = start;
     int row, clo;
     printf("输入一个大写字母：\n");
     scanf_s("%c", &end);
     printf("  字母金字塔\n");
     for ( row=; row <= end-start; row++,ch = start)
     {
         for (clo = ;clo < end - start - row;clo++)
             printf(" ");
         for (int k = ;k <= row;k++)
         {
             printf("%c", ch);
             ch++;
         }
         ch -= ;
         for (int c = ;c < row;c++)
         {
                 printf("%c", ch);
             ch--;
         }
         printf("\n");
     }
     getchar();
     getchar();
     return ;
 }
 /**/
 #include <stdio.h>
 int main( void )
 {
     int start, end;
     printf("输入开始的数字：\n");
     scanf_s("%d", &start);
     printf("输入结束数字：\n");
     scanf_s("%d", &end);
     printf("原数\t平方\t立方\n");
     for (start;start <= end;start++)
     {
         printf("%d\t%d\t%d\n", start, start*start, start*start*start);
     }
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<string.h>
 #define SIZE 40
 int main(void)
 {
     char word[SIZE];
     int i;
     printf("请输入一个单词：\n");
     scanf_s("%s", word, );
     printf("该单词有%d个字母，单词是%s\n", strlen(word), word);
     printf("倒序为：");
     for (i = strlen(word - );i >= ;i--)//strlen(word - 1)跳过字符串后面的空格
         printf("%c", word[i]);
     printf("\n");
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     double a, b;
     int status;//输入状态
     printf("输入2个浮点数（输入q退出）：\n");
     while (scanf_s("%lf%lf", &a, &b) == )//验证是否输入了2个值
     {
         printf("结果是%.3lf", (a - b) / (a*b));
         printf("继续输入2个浮点数（输入q退出）：\n");
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 float result(float a, float b);
 int main(void)
 {
     double a, b;
     int status;//输入状态
     printf("输入2个浮点数（输入q退出）：\n");
     while (scanf_s("%lf%lf", &a, &b) == )//验证是否输入了2个值
     {
         printf("结果是%.3lf", result(a,b));
         printf("继续输入2个浮点数（输入q退出）：\n");
     }
     getchar();
     return ;
 }
 float result(float a, float b)
 {
     float result;//result名称不唯一
     result = (a - b) / (a*b);
     return result;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int up, down;//上限和下限
     printf("输入上限整数和下限整数：\n");
     scanf_s("%d %d", &up, &down);
     while (up>down)
     {
         int sum = ;//初始化平方和sum
         for (int i = sum;i <= up;i++)
             sum = sum + i * i;
         printf("平方和从%d到%d是%d\n", up*up, down*down, sum);
         printf("继续输入上限整数和下限整数：\n");
         scanf_s("%d %d", &up, &down);
     }
     printf("结束！\n");
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define SIZE 8
 int main(void)
 {
     int a[SIZE];
     int i;
     for ( i = ; i < SIZE; i++)
         scanf_s("%d", &a[i]);
         for (i = SIZE - ;i >= ;i--)
             printf("%d", a[i]);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int times;
     float count1 = 1.0f;//分母
     float count2 = 1.0f;//分母
     float sum1 = 0.0;
     float sum2 = 0.0;
     printf("输入计算次数(输入0或负数退出):\n");
     scanf_s("%d", &times);
     for (int i = ;i <= times;i++, count1++)
         sum1 = sum1 + 1.0 / count1;
     for (int j = ;j <= times;j++, count2++)
     {
         if (j%==)
         {
             sum2 = sum2 - 1.0 / count2;
         }
         else
         {
             sum2 = sum2 + 1.0 / count2;
         }
     }
     printf("第一个公式的计算结果为：%f\n", sum1);
     printf("第二个公式的计算结果为：%f\n", sum2);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define SIZE 8
 int main(void)
 {
     int arry[SIZE];
     int i, n;
     for (i = , n = ;i < SIZE;i++, n *= )
         arry[i] = n;
     i = ;
     do
     {
         printf("%d\n", arry[i]);
         i++;
     } while (i<SIZE);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define SIZE 8
 int main(void)
 {
     double arry1[SIZE];
     double arry2[SIZE];
     int i;
 
     printf("输入值：\n");
     for (i = ;i < SIZE;i++)
         scanf_s("%lf", &arry1[i]);//读入第一个数组
     arry2[] = arry1[];//初始化第二个数组
     for (i = ;i < SIZE;i++)
         arry2[i] = arry2[i - ] + arry1[i];//计算第二个元组各数之和
     for (i = ;i < SIZE;i++)
         printf("%8.2lf", arry1[i]);
     printf("\n");
     for (i = ;i < SIZE;i++)
         printf("%8.2lf", arry2[i]);
 
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define SIZE 255
 int main(void)
 {
     char arry[SIZE];
     int i = -;
     printf("输入一个单词：\n");
     do
     {
         i++;//由arry[0]开始循环读入
         scanf_s("%c", &arry[i]);
     } while (arry[i]!='\n');
     for (;i >= ;i--)
         printf("%c", arry[i]);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define Daphne_RATE 0.10    //Daphne利率
 #define Deiedre_RATE 0.05   //Deiedre利率
 #define MONEY 100.0        //投资100元
 int main(void)
 {
     int year=;
     double Daphne_money=MONEY;   //Daphne的投资额
     double Deiedre_money=MONEY;  //Deiedre的投资额
     while (Deiedre_money <= Daphne_money)   //当Deiedre投资额超过Daphne的投资额退出循环
     {
         year++;
         Daphne_money = Daphne_money + MONEY * Daphne_RATE;
         Deiedre_money = Deiedre_money + Deiedre_money * Deiedre_RATE;
     }
     printf("用了%d年Deiedre的投资额超过Daphne的投资额\n", year);
     printf("Daphne的投资额为：%f\tDeiedre的投资额为%f\n", Daphne_money, Deiedre_money);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define RATE 0.08
 int main(void)
 {
     double money = ;
     int year = ;
     while (money>)
     {
         year++;
         money = money + money * RATE;
         money = money - ;
     }
     printf("%d年后Chuckie会取完账户里的钱\n", year);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define DB_NUMBER 150    //邓巴数
 int main(void)
 {
     int weeks = ;
     int friends = ;
     while (friends<DB_NUMBER)
     {
         friends = (friends - weeks) * ;
         printf("%d周后，Rabnud博士有%d个朋友\n", weeks, friends);
         weeks++;
     }
     getchar();
     return ;
 }

 /*****编程练习7*****/
 /**/
 #include<stdio.h>
 int main(void)
 {
     char  ch;
     int spa_count=, lin_count=, oth_count=;   //空格数，换行符数，其他字符数
     printf("输入字符进行统计（输入字符‘#’退出程序）：\n");
     while ((ch=getchar())!='#')
     {
         if (ch == ' ')
             spa_count++;
         else if (ch == '\n')
             lin_count++;
         else
             oth_count++;
     }
     printf("你输入的字符中空格数有%d个，换行符有%d个，其他字符数有%d个\n", spa_count, lin_count, oth_count);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch;
     const int line = ;
     int chsum = ;//统计字符数
     printf("输入字符进行统计（输入‘#’字符结束）：\n");
     while ((ch=getchar())!='#')
     {
         printf("%c:%d\t", ch, ch);
         chsum++;
         if (chsum%line == )
             printf("\n");
     }
     printf("\n");
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int a;
     int ou_count = ;//偶数个数
     int ji_count = ;//奇数个数
     int ou_sum = ;//偶数的和
     int ji_sum = ;//奇数和
     float ou_average;//偶数平均值
     float ji_average;//奇数平均值
     printf("输入整数进行计算（输入‘0’结束）：");
     while (scanf_s("%d", &a) ==  && a != )
     {
         if (a %  == )
         {
             ou_count++;
             ou_sum += a;
         }
         else
         {
             ji_count++;
             ji_sum += a;
         }
     }
         printf("偶数个数：%d\n", ou_count);
         if (ou_count>)
         {
             ou_average = ou_sum / ou_count;
             printf("偶数平均值为：%.2f\n", ou_average);
         }
         printf("奇数个数：%d\n", ji_count);
         if (ji_count>)
         {
             ji_average = ji_sum / ji_count;
             printf("奇数平均值为：%.2f\n", ji_average);
         }
     printf("结束\n");
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch;
     int count1=;//替换句号的次数
     int count2=;//替换感叹号的次数
     printf("输入字符进行统计(输入‘#’结束)：\n");
     while ((ch=getchar())!='#')
     {
         if (ch == '.')
         {
             putchar('!');
             count1++;
         }
         else if (ch == '!')
         {
             putchar('!');
             putchar('!');
             count2++;
         }
         else
             putchar(ch);
     }
     printf("\n'!'替代'.'进行了%d次\n", count1);
     printf("'!!'替代'！'进行了%d次\n", count2);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch;
     int count1 = ;//替换句号的次数
     int count2 = ;//替换感叹号的次数
     printf("输入字符进行统计(输入‘#’结束)：\n");
     while ((ch = getchar()) != '#')
     {
         switch (ch)
         {
         case'.':
             putchar('!');
             count1++;
             break;
         case'!':
             putchar('!');
             putchar('!');
             count2++;
             break;
         default:
             putchar(ch);
         }
     }
     printf("\n'!'替代'.'进行了%d次\n", count1);
     printf("'!!'替代'！'进行了%d次\n", count2);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch;
     char fir, sec;//第一个接收到的字符和第二个字符
     int count = ;//ei出现的次数
     printf("输入进行统计(输入‘#’结束)：\n");
     while ((ch=getchar())!='#')
     {
         if (ch=='e')
         {
             fir = ch;
             continue;
         }
         if (ch=='i')
         {
             sec = ch;
 
             if (fir == 'e'&&sec == 'i')
                 count++;                //判断前一个字符是‘e’，第二个是‘i’，则次数加1
             //初始化fir和sec
             fir = 'a';
             sec = 'a';
             continue;
         }
         continue;
     }
     printf("'ei'出现了%d次\n",count);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define BASE_MONEY 10.00//基本工资
 #define BASE_TIME 40//基本加班时间
 #define OVER_TIME 1.5//超过基本时间
 #define MONY1 300//税率分界线1
 #define MONY2 150//税率分界线2
 #define RATE1 0.15//MONY1前的税率
 #define RATE2 0.20//MONY2的税率
 #define RATE3 0.25//剩下的税率
 int main(void)
 {
     double hours;//一周工作时间
     double sum;//工资总数
     double rate_mony;//税金
     double income;//净收入
     printf("输入一周工作小时数：\n");
     scanf_s("%lf", &hours);
     if (hours <= BASE_TIME)
         sum = hours * BASE_MONEY;
     else
         sum = BASE_TIME * BASE_MONEY + (hours - BASE_TIME)*BASE_MONEY*OVER_TIME;
     if (sum <= MONY1)
         rate_mony = sum * RATE1;
     else if (sum <= MONY1 + MONY2)
         rate_mony = MONY1 * RATE1 + (sum - MONY1)*RATE2;
     else
         rate_mony = MONY1 * RATE1 + MONY2 * RATE2 + (sum - MONY1 - MONY2)*RATE3;
     income = sum - rate_mony;
     printf("工资总额是：%.2lf\t税金是：%.2lf\t净收入是：%.2lf\n", sum, rate_mony, income);
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define BASE_TIME 40     //基本加班时间
 #define OVER_TIME 1.5    //超过基本时间
 #define MONY1 300       //税率分界线1
 #define MONY2 150          //税率分界线2
 #define BASE_LEVEL1 8.75
 #define BASE_LEVEL2 9.33
 #define BASE_LEVEL3 10.00
 #define BASE_LEVEL4 11.20
 #define RATE1 0.15             //MONY1前的税率
 #define RATE2 0.20            //MONY2的税率
 #define RATE3 0.25           //剩下的税率
 int main(void)
 {
     int choice;
     double basy_money;
     double hours;            //一周工作时间
     double sum;             //工资总数
     double rate_money;      //税金
     double income;        //净收入
     printf("*******************************************************\n");
     printf("输入与薪资或操作对应的编号进行操作：\n");
     printf("1) $8.75/hours      \t2) $9.33/hours\n");
     printf("3) $10.00/hours     \t4) $11.20/hours\n");
     printf("5) 退出\n");
     printf("*******************************************************\n");
     while (scanf_s("%d",&choice) ==  && choice != )
     {
         switch (choice)
         {
         case :
             basy_money = BASE_LEVEL1;
             break;
         case :
             basy_money = BASE_LEVEL2;
             break;
         case :
             basy_money = BASE_LEVEL3;
             break;
         case :
             basy_money = BASE_LEVEL4;
             break;
         default:
             printf("请输入1-4数字进行选择（输入数字5退出）。\n请输入正确的数字\n");
             continue;
         }
         printf("输入一周工作小时数：\n");
         scanf_s("%lf", &hours);
         if (hours <= BASE_TIME)
             sum = basy_money * hours;
         else
             sum = BASE_TIME * basy_money + (hours - BASE_TIME)*basy_money*OVER_TIME;
         if (sum <= MONY1)
             rate_money = sum * RATE1;
         else if (sum <= (MONY1 + MONY2))
             rate_money = MONY1 * RATE1 + (sum - MONY1) * RATE2;
         else
             rate_money = MONY1 * RATE1 + MONY2 * RATE2 + (sum - MONY1 - MONY2)*RATE3;
         income = sum - rate_money;
         printf("工资总额是：%.2lf\t税金是：%.2lf\t净收入是：%.2lf\n", sum, rate_money, income);
         printf("输入下一个数字继续\n");
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<stdbool.h>
 int main(void)
 {
     int limit;//输入的数
     int num;
     int div;
     bool numIsPrime;   //判断是否为素数
     printf("输入正整数：");
     while (scanf_s("%d",&limit) ==  && limit > )
     {
         if (limit > )
             printf("以下为素数：\n", limit);
         else
             printf("没有素数\n");
         for (num= ; num <= limit; num++)
         {
             for (div = , numIsPrime = true;(div*div) <= num;div++)
                 if (num%div == )
                     numIsPrime = false;
             if (numIsPrime)
                 printf("%d是素数。\n", num);
         }
         printf("输入正整数(输入q退出)：");
     }
     printf("结束\n");
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define LEVEL1 17850
 #define LEVEL2 23900
 #define LEVEL3 29750
 #define LEVEL4 14875
 #define RATE1 0.15
 #define RATE2 0.28
 int main(void)
 {
     int choice;             //选择号码
     long level;            //税金等级
     double income;         //收入
     double taxmoney;       //税金
     printf("****************************************************************************\n");
     printf("输入类别编号：\n");
     printf("1) 单身   \t2) 户主   \t3) 已婚，共有   \t4) 已婚，离异\n");
     printf("5) 退出\n");
     printf("****************************************************************************\n");
     while (scanf_s("%d",&choice) ==  && choice != )
     {
         switch (choice)
         {
         case :
             level = LEVEL1;
             break;
         case :
             level = LEVEL2;
             break;
         case :
             level = LEVEL3;
             break;
         case :
             level = LEVEL4;
             break;
         default:
             printf("请输入1-4数字进行选择（输入数字5退出）。\n请输入正确的数字\n");
             break;
         }
         printf("请输入你的收入：");
         scanf_s("%lf", &income);
         if (income <= level)
             taxmoney = income * RATE1;
         else
             taxmoney = level * RATE1 + (income - level)*RATE2;
         printf("你的税金为%.2lf元\n", taxmoney);
         printf("继续输入选择（输入5退出）：\n");
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #define Y_PRICE 2.05        //洋蓟 单价
 #define T_PRICE 1.15        //甜菜
 #define H_PRICE 1.09       //胡萝卜
 #define DISCOUNT 0.05      //折扣优惠
 
 #define WEIGHT_LEVEL1 5      //重量层次
 #define WEIGHT_LEVEL2 20
 
 #define TRANS_LEVEL1 6.5      //运费和包装费层次
 #define TRANS_LEVEL2 14
 
 #define TRANS_LEVEL3 0.5       //额外增费
 int main(void)
 {
     char ch;       //选择字符
     float input;     //输入磅数
     float y_weight = ;   //洋蓟磅数
     float t_weight = ;    //甜菜磅数
     float h_weight = ;     //胡萝卜磅数
     float total_weight;   //总重
     float cost;            //花费
     float total_cost;         //总花费：买菜+运费
     float discount;           //折扣
     float tran_cost;         //运费
     float total_all;
     printf("************************************************\n");
     printf("输入编号进行选择：\n");
     printf("a:洋蓟\tb:甜菜\tc:胡萝卜\nq:退出并打印账单\n");
     printf("************************************************\n");
     while ((ch = getchar()) != 'q')
     {
         if (ch == '\n')
             continue;
         while (getchar() != '\n')
             continue;
         switch (ch)
         {
         case 'a':
             printf("输入洋蓟的磅数：");
             scanf_s("%f", &input);
             y_weight = y_weight + input;
             break;
         case 'b':
             printf("输入甜菜的磅数：");
             scanf_s("%f", &input);
             t_weight = t_weight + input;
             break;
         case 'c':
             printf("输入胡萝卜的磅数：");
             scanf_s("%f", &input);
             h_weight = h_weight + input;
             break;
         default:
             printf("输入错误,请输入a,b,c选择蔬菜，q退出\n");
             break;
         }
         printf("继续输入进行购物\n");
     }
     total_weight = y_weight + t_weight + h_weight;
     cost = y_weight * Y_PRICE + t_weight * T_PRICE + h_weight * H_PRICE;
     if (cost >= )
         discount = cost * DISCOUNT;
     else
         discount = ;
     if (total_weight <= )
         tran_cost = ;
     else if (total_weight <= WEIGHT_LEVEL1)
         tran_cost = TRANS_LEVEL1;
     else if (total_weight <= WEIGHT_LEVEL2)
         tran_cost = TRANS_LEVEL2;
     else
         tran_cost = TRANS_LEVEL2 + TRANS_LEVEL3 * total_weight;
     total_all = cost + tran_cost - discount;
     printf("你的订单如下：\n");
     printf("2.05美元/磅的洋蓟订购了%.2f磅\n", y_weight);
     printf("1.15美元/磅的甜菜订购了%.2f磅\n", t_weight);
     printf("1.09美元/磅的胡萝卜订购了%.2f磅\n", h_weight);
     printf("买蔬菜的费用为：%.2f\n", cost);
     if(cost>)
         printf("折扣为：%.2f\n", discount);
     printf("运费和包装费为：%.2f\n", tran_cost);
     printf("所有费用为：%.2f\n", total_all);
     getchar();
     getchar();
     return ;
 }

 /****编程练习8****/
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch;
     int a = ;
     while ((ch=getchar())!=EOF)
         a++;
     printf("读取到%d个字符。\n", a);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch;
     int i=;            //统计每行的值
     while ((ch=getchar())!=EOF)
     {
         if (ch == '\n')
         {
             putchar('\\');
             putchar('n');
             printf(" %d\n", ch);
             i = ;
         }
         else if (ch == '\t')
         {
             putchar('\\');
             putchar('t');
             printf("%d\n", ch);
         }
         else if (ch < ' ')
         {
             putchar('^');
             putchar(ch + );
             printf("%d\t", ch);
         }
         else
             printf("%c %d\t", ch, ch);
         if (++i == )
         {
             printf("\n");
             i = ;
         }
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 int main(void)
 {
     int ch;
                                  //统计个数，用不到负数
     unsigned A_count = ;        //大写
     unsigned a_count = ;        //小写
     unsigned oth_count = ;       //其他字符个数
     while ((ch=getchar())!=EOF)
     {
         //if (isupper(ch))         //用isupper()函数判断是否为大写
         if(ch>='A'&&ch<='Z')       //可以用该行替换上一行，这种方法不用再调用ctype.h
             A_count++;
         else if (islower(ch))      //用islower()函数判断是否为小写
             a_count++;
         else
             oth_count++;
     }
     printf("输入中大写字母有%d个\n", A_count);
     printf("小写字母有%d个\n", a_count);
     printf("其他字符有%d个\n", oth_count);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 #include<stdbool.h>
 int main(void)
 {
     char ch;
     int words = , count = ;      //单词   字母总数
     bool inword = false;           //判断是否是一个单词
     float average;
     while ((ch=getchar())!=EOF)
     {
         if (isalpha(ch))
             count++;               //如果是个字符，字母+1
         if (!isspace(ch) && !inword)
         {
             inword = true;
             words++;               //如果不是空格且inword为true，单词+1
         }
         if (isspace(ch) && inword)
             inword = false;           //如果是个空格，且inword为true，此时并不是个完整单词，需要初始化inword
         if (ispunct(ch))
             continue;               //如果是字符，中断本次循环
     }
     average = count / words;
     printf("平均每个单词有%.2f个字母", average);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int high = ;
     int low = ;
     int    guess=(low+high)/;
     char response;
     printf("你在1-100中选一个数字，我能猜出那个数字！");
     printf("\n如果我回答正确，就输入'y'");
     printf("\n如果我猜的数太高，就输入'h'");
     printf("\n如果我猜的数太小，就输入'l'\n");
     printf("你选择的数字是 %d?\n", guess);
     while ((response=getchar())!='y')
     {
         if (response == '\n')
             continue;
         if (response != 'h'&&response != 'l')
         {
             printf("对不起，输入错误！请重新输入！\n");
             continue;
         }
         if (response == 'h')
             high = guess - ;
         else if (response == 'l')
             low = guess + ;
         guess = (high + low) / ;
         printf("你选择的数字是 %d?\n", guess);
     }
     printf("哈哈！我猜对了！\n");
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 char get_first(void);
 int main(void)
 {
     char ch;
     ch = get_first();
     putchar(ch);
     getchar();
     return ;
 }
 char get_first(void)
 {
     char ch;
     ch = getchar();
     while (isspace(ch))
         ch = getchar();
     while (getchar() != '\n')
         continue;
     return ch;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 #include<math.h>
 #define BASY_MONEY1 8.75       //基本工资
 #define BASY_MONEY2 9.33
 #define BASY_MONEY3 10.00
 #define BASY_MONEY4 11.20
 
 #define BASY_TIME 40         //基本工作时间
 #define EXTR_TIME 1.5         //加班
 
 #define LIN_MONEY1 300       //税率分界线
 #define LIN_MONEY2 150       
 
 #define RATE1 0.15            //税率
 #define RATE2 0.20
 #define RATE3 0.25
 int get_first(void);          //创建函数，如果输入为空，则丢弃
 int main(void)
 {
     char ch;
     double basy_money;
     double hours;
     double sum;           //工资总数
     double rate_money;    //税金
     double income;        //净收入
     printf("*******************************************************\n");
     printf("输入与薪资或操作对应的编号进行操作：\n");
     printf("a) $8.75/hours      \tb) $9.33/hours\n");
     printf("c) $10.00/hours     \td) $11.20/hours\n");
     printf("q) 退出\n");
     printf("*******************************************************\n");
     while ((ch=get_first())!='q')   //调用get_first()函数
     {
         if (ch =='\n')
             continue;
         ch = tolower(ch);       //将大写字母转为小写
         switch (ch)
         {
         case 'a':
             basy_money = BASY_MONEY1; break;
         case 'b':
             basy_money = BASY_MONEY2; break;
             case 'c':
                 basy_money = BASY_MONEY3; break;
             case 'd':
                 basy_money = BASY_MONEY4; break;
         default:
             printf("请输入a-d进行选择（输入q退出）。\n请输入正确的数字\n"); break;
         }
         printf("输入一周工作小时数：\n");
         scanf_s("%lf", &hours);
         if (hours <= BASY_TIME)
             sum = basy_money * hours;
         else
             sum = basy_money * BASY_TIME + (hours - BASY_TIME)*basy_money*EXTR_TIME;
         if (sum <= LIN_MONEY1)
             rate_money = sum * RATE1;
         else if (sum <= (LIN_MONEY1 + LIN_MONEY2))
             rate_money = LIN_MONEY1*RATE1 + (sum - LIN_MONEY1)*RATE2;
         else
             rate_money = LIN_MONEY1 * RATE1 + LIN_MONEY2 * RATE2 + BASY_MONEY2 + (sum - LIN_MONEY1 - LIN_MONEY2)*RATE3;
         income = sum - rate_money;
         printf("工资总额是：%.2lf\t税金是：%.2lf\t净收入是：%.2lf\n", sum, rate_money, income);
         printf("输入下一个数字继续\n");
     }
     getchar();
     return ;
 }
 int get_first(void)
 {
     int ch;
     ch = getchar();
     while (isspace(ch))
         ch = getchar();
     while (getchar() != '\n')
         continue;
     return ch;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 int get_first(void);
 float get_num(void);
 int main(void)
 {
     char ch;
     float first, second;
     printf("输入你想进行运算的选项：\n");
     printf("a.加法\ts.减法\n");
     printf("m.乘法\td.除法\n");
     printf("q.退出\n");
     while ((ch=get_first())!='q')
     {
         ch = tolower(ch);
         if (ch != 'a'&& ch != 's'&& ch != 'm'&& ch != 'd')
         {
             printf("你只能输入a,s,m,d,q中的一个:");
             continue;
         }
         printf("输入第一个数：");
         first = get_num();
         printf("输入第二个数：");
         second = get_num();
         if (ch == 'd')
         {
             while (second == )
             {
                 printf("输入一个大于0的数：");
                 second = get_num();
             }
         }
         switch (ch)
         {
         case 'a':
             printf("%.1f+%.1f=%.1f\n", first, second, first + second); break;
         case 's':
             printf("%.1f-%.1f=%.1f\n", first, second, first - second); break;
         case 'm':
             printf("%.1f*%.1f=%.1f\n", first, second, first*second); break;
         case 'd':
             printf("%.1f/%.1f=%.1f\n", first, second, first / second); break;
         default:
             ;
             break;
         }
         printf("输入你想进行运算的选项：\n");
         printf("a.加法\ts.减法\n");
         printf("m.乘法\td.除法\n");
         printf("q.退出\n");
     }
     getchar();
     return ;
 }
 int get_first(void)
 {
     int ch;
     while ((ch = getchar()) == ' ' || ch == '\t' || ch == '\n')
         continue;
     while (getchar() != '\n')
         continue;
     return ch;
 }
 float get_num(void)
 {
     float input;
     char ch;
     while (scanf_s("%f",&input)!=)
     {
         while ((ch = getchar()) != '\n')
             putchar(ch);
         printf("%c不是数字\n请输入例如2.5，-1.78E8，3之类的数字：",ch);
     }
     return input;
 }

 /****编程练习8****/
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch;
     int a = ;
     while ((ch=getchar())!=EOF)
         a++;
     printf("读取到%d个字符。\n", a);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     char ch;
     int i=;            //统计每行的值
     while ((ch=getchar())!=EOF)
     {
         if (ch == '\n')
         {
             putchar('\\');
             putchar('n');
             printf(" %d\n", ch);
             i = ;
         }
         else if (ch == '\t')
         {
             putchar('\\');
             putchar('t');
             printf("%d\n", ch);
         }
         else if (ch < ' ')
         {
             putchar('^');
             putchar(ch + );
             printf("%d\t", ch);
         }
         else
             printf("%c %d\t", ch, ch);
         if (++i == )
         {
             printf("\n");
             i = ;
         }
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 int main(void)
 {
     int ch;
                                  //统计个数，用不到负数
     unsigned A_count = ;        //大写
     unsigned a_count = ;        //小写
     unsigned oth_count = ;       //其他字符个数
     while ((ch=getchar())!=EOF)
     {
         //if (isupper(ch))         //用isupper()函数判断是否为大写
         if(ch>='A'&&ch<='Z')       //可以用该行替换上一行，这种方法不用再调用ctype.h
             A_count++;
         else if (islower(ch))      //用islower()函数判断是否为小写
             a_count++;
         else
             oth_count++;
     }
     printf("输入中大写字母有%d个\n", A_count);
     printf("小写字母有%d个\n", a_count);
     printf("其他字符有%d个\n", oth_count);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 #include<stdbool.h>
 int main(void)
 {
     char ch;
     int words = , count = ;      //单词   字母总数
     bool inword = false;           //判断是否是一个单词
     float average;
     while ((ch=getchar())!=EOF)
     {
         if (isalpha(ch))
             count++;               //如果是个字符，字母+1
         if (!isspace(ch) && !inword)
         {
             inword = true;
             words++;               //如果不是空格且inword为true，单词+1
         }
         if (isspace(ch) && inword)
             inword = false;           //如果是个空格，且inword为true，此时并不是个完整单词，需要初始化inword
         if (ispunct(ch))
             continue;               //如果是字符，中断本次循环
     }
     average = count / words;
     printf("平均每个单词有%.2f个字母", average);
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 int main(void)
 {
     int high = ;
     int low = ;
     int    guess=(low+high)/;
     char response;
     printf("你在1-100中选一个数字，我能猜出那个数字！");
     printf("\n如果我回答正确，就输入'y'");
     printf("\n如果我猜的数太高，就输入'h'");
     printf("\n如果我猜的数太小，就输入'l'\n");
     printf("你选择的数字是 %d?\n", guess);
     while ((response=getchar())!='y')
     {
         if (response == '\n')
             continue;
         if (response != 'h'&&response != 'l')
         {
             printf("对不起，输入错误！请重新输入！\n");
             continue;
         }
         if (response == 'h')
             high = guess - ;
         else if (response == 'l')
             low = guess + ;
         guess = (high + low) / ;
         printf("你选择的数字是 %d?\n", guess);
     }
     printf("哈哈！我猜对了！\n");
     getchar();
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 char get_first(void);
 int main(void)
 {
     char ch;
     ch = get_first();
     putchar(ch);
     getchar();
     return ;
 }
 char get_first(void)
 {
     char ch;
     ch = getchar();
     while (isspace(ch))
         ch = getchar();
     while (getchar() != '\n')
         continue;
     return ch;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 #include<math.h>
 #define BASY_MONEY1 8.75       //基本工资
 #define BASY_MONEY2 9.33
 #define BASY_MONEY3 10.00
 #define BASY_MONEY4 11.20
 
 #define BASY_TIME 40         //基本工作时间
 #define EXTR_TIME 1.5         //加班
 
 #define LIN_MONEY1 300       //税率分界线
 #define LIN_MONEY2 150       
 
 #define RATE1 0.15            //税率
 #define RATE2 0.20
 #define RATE3 0.25
 int get_first(void);          //创建函数，如果输入为空，则丢弃
 int main(void)
 {
     char ch;
     double basy_money;
     double hours;
     double sum;           //工资总数
     double rate_money;    //税金
     double income;        //净收入
     printf("*******************************************************\n");
     printf("输入与薪资或操作对应的编号进行操作：\n");
     printf("a) $8.75/hours      \tb) $9.33/hours\n");
     printf("c) $10.00/hours     \td) $11.20/hours\n");
     printf("q) 退出\n");
     printf("*******************************************************\n");
     while ((ch=get_first())!='q')   //调用get_first()函数
     {
         if (ch =='\n')
             continue;
         ch = tolower(ch);       //将大写字母转为小写
         switch (ch)
         {
         case 'a':
             basy_money = BASY_MONEY1; break;
         case 'b':
             basy_money = BASY_MONEY2; break;
             case 'c':
                 basy_money = BASY_MONEY3; break;
             case 'd':
                 basy_money = BASY_MONEY4; break;
         default:
             printf("请输入a-d进行选择（输入q退出）。\n请输入正确的数字\n"); break;
         }
         printf("输入一周工作小时数：\n");
         scanf_s("%lf", &hours);
         if (hours <= BASY_TIME)
             sum = basy_money * hours;
         else
             sum = basy_money * BASY_TIME + (hours - BASY_TIME)*basy_money*EXTR_TIME;
         if (sum <= LIN_MONEY1)
             rate_money = sum * RATE1;
         else if (sum <= (LIN_MONEY1 + LIN_MONEY2))
             rate_money = LIN_MONEY1*RATE1 + (sum - LIN_MONEY1)*RATE2;
         else
             rate_money = LIN_MONEY1 * RATE1 + LIN_MONEY2 * RATE2 + BASY_MONEY2 + (sum - LIN_MONEY1 - LIN_MONEY2)*RATE3;
         income = sum - rate_money;
         printf("工资总额是：%.2lf\t税金是：%.2lf\t净收入是：%.2lf\n", sum, rate_money, income);
         printf("输入下一个数字继续\n");
     }
     getchar();
     return ;
 }
 int get_first(void)
 {
     int ch;
     ch = getchar();
     while (isspace(ch))
         ch = getchar();
     while (getchar() != '\n')
         continue;
     return ch;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 int get_first(void);
 float get_num(void);
 int main(void)
 {
     char ch;
     float first, second;
     printf("输入你想进行运算的选项：\n");
     printf("a.加法\ts.减法\n");
     printf("m.乘法\td.除法\n");
     printf("q.退出\n");
     while ((ch=get_first())!='q')
     {
         ch = tolower(ch);
         if (ch != 'a'&& ch != 's'&& ch != 'm'&& ch != 'd')
         {
             printf("你只能输入a,s,m,d,q中的一个:");
             continue;
         }
         printf("输入第一个数：");
         first = get_num();
         printf("输入第二个数：");
         second = get_num();
         if (ch == 'd')
         {
             while (second == )
             {
                 printf("输入一个大于0的数：");
                 second = get_num();
             }
         }
         switch (ch)
         {
         case 'a':
             printf("%.1f+%.1f=%.1f\n", first, second, first + second); break;
         case 's':
             printf("%.1f-%.1f=%.1f\n", first, second, first - second); break;
         case 'm':
             printf("%.1f*%.1f=%.1f\n", first, second, first*second); break;
         case 'd':
             printf("%.1f/%.1f=%.1f\n", first, second, first / second); break;
         default:
             ;
             break;
         }
         printf("输入你想进行运算的选项：\n");
         printf("a.加法\ts.减法\n");
         printf("m.乘法\td.除法\n");
         printf("q.退出\n");
     }
     getchar();
     return ;
 }
 int get_first(void)
 {
     int ch;
     while ((ch = getchar()) == ' ' || ch == '\t' || ch == '\n')
         continue;
     while (getchar() != '\n')
         continue;
     return ch;
 }
 float get_num(void)
 {
     float input;
     char ch;
     while (scanf_s("%f",&input)!=)
     {
         while ((ch = getchar()) != '\n')
             putchar(ch);
         printf("%c不是数字\n请输入例如2.5，-1.78E8，3之类的数字：",ch);
     }
     return input;
 }

 /*********编程练习9***********/
 /*复习题9*/
 #include<stdio.h>
 void mennu(void);        //菜单函数
 int limt(int up, int down);    //上下限函数
 int main(void)
 {
     int ch;
     mennu();
     while ((ch=limt(,))!=)
     {
         printf("%d一个正确的选择！\n",ch);
         mennu();
     }
     getchar();
     getchar();
     getchar();
     return ;
 }
 void mennu(void)
 {
     printf("请选择列表中对应的数字：\n");
     printf("1) 复制文件 \t2) 移动文件\n");
     printf("3) 删除文件 \t4) 退出\n");
     printf("输入你选择的数字：\n");
 }
 int limt(int up, int down)
 {
     int input;
     int a=scanf_s("%d", &input);
     while (a==&&(input > up || input < down))
     {
         printf("输入数值超过限制!\n");
         mennu();
         scanf_s("%d", &input);
     }
     if (a!=)
     {
         printf("没有数字输入!\n");
         input = ;
     }
     return input;
 }
 /*编程练习1*/
 #include<stdio.h>
 double min(double x, double y);
 int main(void)
 {
     double a, b;
     printf("输入两个小数，将输出较小的值（输入q退出）：\n");
     while (scanf_s("%lf %lf", &a, &b)==)
     {
         printf("%lf和%lf中较小的数是：%lf", a, b, min(a, b));
         printf("继续输入进行比较（输入q退出）：\n");
     }
     getchar();
     return ;
 }
 double min(double x, double y)
 {
     return x < y ? x : y;
 }
 /**/
 #include<stdio.h>
 void chline(char ch, int i, int j);
 int main(void)
 {
     char c;
     int row;
     int clum;
     printf("该程序要求输入一个字符并按输入的行列数打印\n");
     printf("输入你想打印的字符：");
     scanf_s("%c", &c);
     printf("输入你想打印的行和列（用空格分开）：");
     scanf_s("%d %d", &row, &clum);
     printf("\n");
     chline(c, row, clum);
     getchar();
     getchar();
     return ;
 
 }
 void chline(char ch, int i, int j)
 {
     for (int x = ; x < i; x++)
     {
         for (int y = ; y < j; y++)
             putchar(ch);
         putchar('\n');
     }
 }
 /**/
 #include<stdio.h>
 void chline(char ch, int i, int j);
 int main(void)
 {
     char ch;
     int row, clo;
     printf("输入想要打印的字符：");
     while ((ch=getchar())!='#')
     {
         if (ch == '\n')
             continue;
         printf("输入想要打印的次数和行数：");
         if (scanf_s("%d %d", &clo, &row) != )
             break;
         chline(ch, clo, row);
         printf("继续输入下一个想打印的字符（输入#退出）：");
     }
     getchar();
     return ;
 }
 void chline(char ch, int i, int j)
 {
     for (int x = ; x < i; x++)
             {
                 for (int y = ; y < j; y++)
                     putchar(ch);
                 putchar('\n');
             }
 }
 /**/
 #include<stdio.h>
 double Har_average(double num1, double num2);        //调和平均数
 int main(void)
 {
     double a = 3.14, b = 3.15, c;
     c=Har_average(a, b);
     printf("%lf", c);
     getchar();
     return ;
 }
 double Har_average(double num1, double num2)
 {
     double down_num1, down_num2, down_avweage;
     down_num1 =  / num1;
     down_num2 =  / num2;
     down_avweage =  / ((down_num1 + down_num2) / );
     return down_avweage;
 }
 /**/
 #include<stdio.h>
 void large_of(double *p1, double *p2);
 int main(void)
 {
     double a, b;
     printf("输入两个值：");
     while (scanf_s("%lf %lf",&a,&b)==)
     {
         large_of(&a, &b);
         printf("交换后的值为%lf和%lf\n", a, b);
         printf("继续输入（输入q退出）：");
     }
     getchar();
     return ;
 }
 void large_of(double *p1, double *p2)
 {
     if (*p1 > *p2)
         *p2 = *p1;
     else
         *p1 = *p2;
 }
 /**/
 #include<stdio.h>
 void change(double *p1, double *p2, double*p3);
 int main(void)
 {
     double a, b, c;
     while (scanf_s("%lf %lf %lf", &a, &b,&c) == )
             {
                 change(&a, &b, &c);
                 printf("交换后的值为%lf和%lf和%f\n", a, b,c);
                 printf("继续输入（输入q退出）：");
             }
             getchar();
             return ;
 }
 void change(double *p1, double *p2, double *p3)
 {
     double max, min, mid;
     max = *p1;
     if (max < *p2)
         max = *p2;
     if (max < *p3)
         max = *p3;
     min = *p1;
     if (min > *p2)
         min = *p2;
     if (min > *p3)
         min = *p3;
     mid = *p1 + *p2 + *p3 - max - min;
     *p1 = min;
     *p2 = mid;
     *p3 = max;
 }
 /**/
 #include<stdio.h>
 #include<ctype.h>
 int report(char ch);
 int main(void)
 {
     char ch;
     int pos;            //数值位置
     printf("请输入字符：");
     while ((ch=getchar())!=EOF)
     {
         if (ch == '\n')
         {
             continue;
         }
         pos = report(ch);
         if (pos == -)
         {
             printf("%c不是字母！\n", ch);
         }
         else
         {
             printf("%c在字母表中的位置是%d!\n", ch, pos);
         }
         printf("继续输入:");
     }
     getchar();
     return ;
 }
 int report(char ch)
 {
     if (isalpha(ch))                 //判断是否为字母
     {
         return toupper(ch) - 'A' + ;       //将小写转换为大写；也可以将大写转换为小写，‘A’要改为‘a’
     }
     else
     {
         return -;
     }
 }
 /**/
 #include<stdio.h>
 double power(double n, int p);
 int main(void)
 {
     double x, xpow;
     int exp;
     printf("输入数字和指数，计算整数幂结果（q退出）：");
     while (scanf_s("%lf %d",&x,&exp)==)
     {
         xpow = power(x, exp);
         if (xpow == )
             continue;
         printf("%.3g的%d次幂为%.5g\n", x, exp, xpow);
         printf("继续输入（q退出）：");
     }
     getchar();
     return ;
 }
 double power(double n, int p)
 {
     double pow = ;
     if (p == )
     {
         if (n==)
         {
             printf("0的0次幂未定义，请输入其它值:\n");
         }
         pow = ;
     }
     else if (p==)
     {
         pow = ;
     }
     else if (p>)
     {
         for (int i = ; i <= p; i++)
         {
             pow *= n;
         }
     }
     else
     {
         pow =  / power(n, -p);     //运用了递归
         ///////不用递归的写法：for(int i=1; i <= -p; i++)
          //////////////////       {
 ////////////////////////////            pow*=n;
 ////////////////////////////         }          //此种方法返回的是 1/pow
     }
     return pow;
 }
 /**/
 ////上题所示/////////
 /**/
 #include<stdio.h>
 void to_base_n(int x, int system);
 int main(void)
 {
     int num;
     int system_num;
     int status;
     printf("输入一个整数：");
     while (scanf_s("%d",&num)==)
     {
         printf("输入进制（2-10）:");
         while ((status=scanf_s("%d",&system_num))==&&(system_num<||system_num>))
         {
             printf("输入进制超过限定值，请输入2-10之间的数字：");
         }
         if (status != )
             break;
         to_base_n(num, system_num);
         printf("\n");
         printf("继续输入一个整数（q退出）：");
     }
     getchar();
     return ;
 }
 void to_base_n(int x, int system)
 {
     int r;
     r = x % system;
     if (x >= system)
     {
         to_base_n(x / system, system);           //递归
     }
     putchar('' + r);           //因为putchar()函数只能输出字符，我们要输出的是字符，所以运用ASCALL码值加上r
 }
 /**/
 #include<stdio.h>
 void Fibonacci(int n);
 int main(void)
 {
     int n;
     printf("输入整数：");
     while ((scanf_s("%d",&n)==))
     {
         Fibonacci(n);
         printf("继续输入（q退出）：");
     }
     getchar();
     return ;
 }
 void Fibonacci(int n)
 {
     int f1, f2, f3;
     printf("斐波那契是：");
     for (int i = ; i <= n; i++)
     {
         if (i == )
         {
             f1 = ;
             printf("%d", f1);
         }
         else if (i==)
         {
             f2 = ;
             printf("%d", f2);
                  }
         else
         {
             f3 = f2 + f1;
             f1 = f2;
             f2 = f3;
             printf("%d", f3);
         }
         putchar(' ');
     }
     putchar('\n');
 }

 /********编程练习10**********/
 /**/
 #include<stdio.h>
 #define MONTHS 12
 #define YEARS 5
 int main(void)
 {
     const float rain[YEARS][MONTHS] =        //2010-2014年降水量
     {
         {4.3,4.3,4.3,3.0,2.0,1.2,0.2,0.2,0.4,2.4,3.5,6.6},
         {8.5,8.2,1.2,1.6,2.4,0.0,5.2,0.9,0.3,0.9,1.4,7.3},
         {9.1,8.5,6.7,4.3,2.1,0.8,0.2,0.2,1.1,2.3,6.1,8.4},
         {7.2,9.9,8.4,3.3,1.2,0.8,0.4,0.0,0.6,1.7,4.3,6.2},
         {7.6,5.6,3.8,2.8,3.8,0.2,0.0,0.0,0.0,1.3,2.6,5.2}
     };
     int year, month;
     float subtot, total;                     //初始化要放在循环中
     printf("年份\t降水量\n");
     for (year = ,total=; year < YEARS; year++)
     {
         for (month = ,subtot = ; month < MONTHS; month++)
             subtot += *(*(rain + year) + month);     //每年每月降水量
         printf("%d\t%.1f\n",  + year, subtot);
         total += subtot;                            //5年总降水量
     }
     printf("\n每年的平均降水量为：%.1f\n", total / YEARS);
     printf("每月5年中平均降水量：\n");
     printf(" 1   2   3   4   5   6   7   8   9   10  11  12\n");
     for (month = ; month < MONTHS; month++)
     {
         for (year = , subtot = ; year < YEARS; year++)
         {
             subtot += *(*(rain + year) + month);
         }
         printf("%4.1f", subtot / YEARS);
     }
     getchar();
     return ;
 }
 /**/
 #include<stdio.h>
 void copy_arr(double target[], double source[], int n);
 void copy_ptr(double *target, double *source, int n);
 void copy_ptrs(double *target, double *source_begin, int *source_end );
 int main(void)
 {
     int i;
     double source[] = { 1.1, 2.2, 3.3, 4.4, 5.5 };
     double target1[];
     double target2[];
     double target3[];
     printf("source: ");
     for ( i = ; i < ; i++)
     {
         printf("%.1lf", source[i]);
         printf(" ");
     }
     putchar('\n');
     copy_arr(target1, source, );
     printf("target1:");
     for (i = ; i < ; i++)
     {
         printf("%.1lf", target1[i]);
         putchar(' ');
     }
     putchar('\n');
     copy_ptr(target2, source, );
     printf("target2:");
     for ( i = ; i < ; i++)
     {
         printf("%.1lf", *(target2 + i));
         putchar(' ');
     }
     putchar('\n');
     copy_ptrs(target3, source, source+);
     printf("target3:");
     for (i = ; i < ; i++)
     {
         printf("%.1lf", target3[i]);
         putchar(' ');
     }
     putchar('\n');
     getchar();
     return ;
 }
 void copy_arr(double target[], double source[], int n)
 {
     for (int i = ; i < n; i++)
     {
         target[i] = source[i];
     }
 }
 void copy_ptr(double *target, double *source, int n)
 {
     for (int i = ; i < n; i++)
     {
         *(target + i) = *(source + i);
     }
 }
 void copy_ptrs(double *target, double *source_begin, int *source_end)
 {
     while (source_begin < source_end)
     {
         *target = *source_begin;
         target++;
         source_begin++;
     }
 }
 /**/
 #include<stdio.h>
 #define SIZE 10
 void show_arr(const arr[], int n);
 int max_arr(const arr[], int n);
 int main(void)
 {
     int arr[SIZE] = { ,,,,,,,,, };
     int max;
     show_arr(arr, SIZE);
     max = max_arr(arr, SIZE);
     printf("%d是数组中的最大值。\n", max);
     getchar();
     return ;
 }
 int max_arr(const arr[], int n)
 {
     int max = arr[];
     for (int i = ; i < n; i++)
     {
         if (max < arr[i])
             max = arr[i];
     }
     return max;
 }
 void show_arr(const arr[], int n)
 {
     for (int i = ; i < n; i++)
     {
         printf("%d", arr[i]);
         putchar(' ');
     }
     putchar('\n');
 }
 /**/
 #include<stdio.h>
 #define SIZE 10
 double max(const arr[], int n);
 void show_arr(const arr[], int n);
 int main(void)
 {
     int arr[SIZE] = { ,,,,,,,,, };
     int max_sub;
     show_arr(arr, SIZE);
     max_sub = max(arr, SIZE);
     printf("最大值的下标是%d\n", max_sub);
     getchar();
     return ;
 }
 double max(const arr[], int n)
 {
     int max = arr[];
     int sub;                 //最大值下标
     for (int i = ; i < n; i++)
     {
         if (max < arr[i])
             max = arr[i];
         sub = i;
     }
     return sub;
 }
 void show_arr(const arr[], int n)
 {
     for (int i = ; i < n; i++)
     {
         printf("%d", arr[i]);
         putchar(' ');
     }
     putchar('\n');
 }
 /**/
 #include<stdio.h>
 #define SIZE 10
 double diff_val(const double arr[], int n);
 int main(void)
 {
     double arr[SIZE] = { ,,,,,,,,, };
     double value;
     value = diff_val(arr, SIZE);
     printf("最大值与最小值的差是%lf\n", value);
     getchar();
     return ;
 }
 double diff_val(const double arr[], int n)
 {
     double max = arr[];
     double min = arr[];
     for (int i = ; i < n; i++)
     {
         if (max < arr[i])
         {
             max = arr[i];
         }
         else if(min>arr[i])
         {
             min = arr[i];
         }
     }
     return max - min;
 }
 /**/
 #include<stdio.h>
 #define SIZE 10
 void reverse(double arr[], int n);
 int main(void)
 {
     double arr[SIZE] = { ,, ,,,,,,, };
     printf("排序前的结果是：");
     for (int i = ; i < SIZE; i++)
     {
         printf("%.2lf", arr[i]);
         putchar(' ');
     }
     putchar('\n');
     reverse(arr, SIZE);
     printf("排序后的结果是：");
     for (int i = ; i < SIZE; i++)
     {
         printf("%.2lf", arr[i]);
         putchar(' ');
     }
     putchar('\n');
     getchar();
     return ;
 }
 void reverse(double arr[], int n)
 {
     for (int i = ; i < n / ; i++)
     {
         double tmp = arr[i];
         arr[i] = arr[n -  - i];
         arr[n -  - i] = tmp;
     }
 }
 /**/
 #include<stdio.h>
 #define ROWS 3    //行
 #define COLS 4    //列
 void copy_arr(double target_arr[][COLS], double source_arr[][COLS], int row);
 int main(void)
 {
     double source_arr[ROWS][COLS] =
     {
         {1.1,2.2,3.3,4.4},
         {2.2,2.3,2.4,2.5},
         {3.3,4.4,5.5,6.6}
     };
     double target_arr[ROWS][COLS];
     copy_arr(target_arr, source_arr, ROWS);
     printf("结果为：\n");
     for (int i = ; i < ROWS; i++)
     {
         for (int j = ; j < COLS; j++)
         {
             printf("%.2lf", target_arr[i][j]);
             putchar(' ');
         }
         putchar('\n');
     }
     getchar();
     return ;
 }
 void copy_arr(double target_arr[][COLS], double source_arr[][COLS], int row)
 {
     for (int i = ; i < row; i++)
     {
         for (int j = ; j < COLS; j++)
         {
             target_arr[i][j] = source_arr[i][j];
         }
     }
 }
 /**/
 #include<stdio.h>
 #define SIZE1 7
 #define SIZE2 3
 void copy_arr(int target_arr[],const int source_arr[], int n);
 int main(void)
 {
     int source_arr[SIZE1] = { ,,,,,, };
     int target_arr[SIZE2];
     int values;
     copy_arr(target_arr, source_arr + , SIZE2);
     for (int i = ; i < SIZE2; i++)
     {
         printf("%d", target_arr[i]);
         putchar(' ');
     }
     printf("\n");
     getchar();
     return ;
 }
 void copy_arr(int target_arr[], const int source_arr[], int n)
 {
     for (int i = ; i < n; i++)
     {
         target_arr[i] = source_arr[i];
     }
 }
 /**/
 #include<stdio.h>
 void copy_arr(int rows, double target_arr[][],double source_arr[][]);
 void show_arr(int rows, double target_arr[][], double source_arr[][]);
 int main(void)
 {
     double source_arr[][] =
     {
         {1.1,2.2,3.3,4.4,5.5},
         {2.2,3.3,4.4,5.5,6.6},
         {3.3,4.4,5.5,6.6,7.7}
     };
     double target_arr[][];
     copy_arr(, target_arr, source_arr);
     show_arr(, target_arr, source_arr);
     getchar();
     return ;
 }
 void copy_arr(int rows, double target_arr[][], double source_arr[][])
 {
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             target_arr[i][j] = source_arr[i][j];
         }
     }
 }
 void show_arr(int rows, double target_arr[][], double source_arr[][])
 {
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             printf("%.2lf", source_arr[i][j]);
             putchar(' ');
         }
     }
     putchar('\n');
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             printf("%.2lf", target_arr[i][j]);
             putchar(' ');
         }
     }
     putchar('\n');
 }
 /**/
 #include<stdio.h>
 void add_arr(int source_arr1[], int source_arr2[], int target_arr[], int n);
 int main(void)
 {
     int    source_arr1[] = { ,,, };
     int source_arr2[] = { ,,, };
     int target_arr[];
     add_arr(source_arr1, source_arr2, target_arr, );
     for (int i = ; i < ; i++)
     {
         printf("%d", target_arr[i]);
         putchar(' ');
     }
     putchar('\n');
     getchar();
     return ;
 }
 void add_arr(int source_arr1[], int source_arr2[], int target_arr[], int n)
 {
     for (int i = ; i < n; i++)
     {
         target_arr[i] = source_arr1[i] + source_arr2[i];
     }
 }
 /**/
 #include<stdio.h>
 void times2_arr(int source_arr[][], int target_arr[][], int rows);
 void show_arr(int source_arr[][], int target_arr[][], int rows);
 int main(void)
 {
     int source_arr[][] =
                             {
                                 {,,,,},
                                 {,,,,},
                                 {,,,,}
                             };
     int target_arr[][];
     times2_arr(source_arr, target_arr, );
     show_arr(source_arr, target_arr, );
     putchar('\n');
     getchar();
     return ;
 }
 void times2_arr(int source_arr[][], int target_arr[][], int rows)
 {
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             target_arr[i][j] = *source_arr[i][j];
         }
     }
 }
 void show_arr(int source_arr[][], int target_arr[][], int rows)
 {
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             printf("%4d", source_arr[i][j]);
             //putchar(' ');
             //putchar(' ');
         }
     }
     putchar('\n');
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             printf("%4d", target_arr[i][j]);
             //putchar(' ');
         }
     }
     putchar('\n');
 }
 /**/
 #include<stdio.h>
 #define YEARS 5
 #define MONTHS 12
 void total_rain(const float rain[][MONTHS], int years);
 void average(const float rain[][MONTHS], int years);
 int main(void)
 {
     const float rain[YEARS][MONTHS] =        //2010-2014年降水量
     {
         {4.3,4.3,4.3,3.0,2.0,1.2,0.2,0.2,0.4,2.4,3.5,6.6},
         {8.5,8.2,1.2,1.6,2.4,0.0,5.2,0.9,0.3,0.9,1.4,7.3},
         {9.1,8.5,6.7,4.3,2.1,0.8,0.2,0.2,1.1,2.3,6.1,8.4},
         {7.2,9.9,8.4,3.3,1.2,0.8,0.4,0.0,0.6,1.7,4.3,6.2},
         {7.6,5.6,3.8,2.8,3.8,0.2,0.0,0.0,0.0,1.3,2.6,5.2}
     };
     total_rain(rain, YEARS);
     printf("JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NEV DEC\n");
     average(rain, YEARS);
     putchar('\n');
     getchar();
     return ;
 }
 void total_rain(const float rain[][MONTHS], int years)
 {
     int i, j;
     float subtotal,total = ;
     for ( i = ; i < years; i++)          //每次循环需要将total归零。因为计算的是每年每月降水量
     {
         for ( j = , subtotal = ; j < MONTHS; j++)
         {
             subtotal += rain[i][j];
         }
         printf("%d\t%.1f\n",  + i, subtotal);
         total += subtotal;
     }
     printf("5年总降水量为%.1f\n", total / years);
 }
 void average(const float rain[][MONTHS], int years)
 {
     int i, j;
     float subtotal;
     for ( i = ; i < MONTHS; i++)
     {
         for ( j = , subtotal = ; j < years; j++)
         {
             subtotal += rain[j][i];
         }
         printf("%-4.1f", subtotal / years);
     }
 }
 /**/
 #include<stdio.h>
 void input_arr(double arr[][], int rows);
 double average_cols(double arr[], int cols);
 double average_all(double arr[][], int rows);
 double max_arr(double arr[][], int rows);
 void show_arr(double arr[][], int rows);
 int main(void)
 {
     double arr[][];
     printf("输入15个浮点值：\n");
     input_arr(arr, );
     putchar('\n');
     for (int i = ; i < ; i++)
     {
         printf("%d组数据的平均值是%lf\n", i+, average_cols(arr[i], ));
     }
     printf("所有数据的平均值是%lf\n", average_all(arr, ));
     printf("15个数据中最大值为：%lf\n", max_arr(arr, ));
     show_arr(arr, );
     getchar();
     return ;
 }
 void input_arr(double arr[][], int rows)
 {
     for (int i = ; i < rows; i++)
     {
         printf("请输入第%d组数据：\n", i + );
         for (int j = ; j < ; j++)
         {
             scanf_s("%lf", &arr[i][j]);
             getchar();
         }
     }
 }
 double average_cols(double arr[], int cols)
 {
     double sum = 0.0;
     for (int i = ; i < cols; i++)
     {
         sum += arr[i];
     }
     return (sum / cols);
 }
 double average_all(double arr[][], int rows)
 {
     double sum = 0.0;
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             sum += arr[i][j];
         }
     }
     return (sum / ( * rows));
 }
 double max_arr(double arr[][], int rows)
 {
     double max = 0.0;
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             if (max<arr[i][j])
             {
                 max = arr[i][j];
             }
         }
     }
     return max;
 }
 void show_arr(double arr[][], int rows)
 {
     for (int i = ; i < rows; i++)
     {
         for (int j = ; j < ; j++)
         {
             printf("%lf", arr[i][j]);
             putchar(' ');
         }
         putchar('\n');
     }
 }
 /**/
 //////////////我的vs2017似乎不支持变长数组，但大致定义如下
 /*#include<stdio.h>
 #define ROWS 3
 #define COLS 5
 void input_arr(int rows,int cols, double arr[rows][cols]);
 double average_cols(int cols,double arr[cols]);
 double average_all(int rows, int cols, double arr[rows][cols]);
 double max_arr(int rows, int cols, double arr[rows][cols]);
 void show_arr(int rows, int cols, double arr[rows][cols]);
 int main(void)
 {
 
     getchar();
     return 0;
 }*/