吴裕雄--天生自然C++语言学习笔记：C++ 实例

C++ 实例 - 输出 "Hello, World!"
#include <iostream>
using namespace std;

int main()
{
    cout << "Hello, World!";
    return ;
}
C++ 实例 - 标准输入输出
#include <iostream>
using namespace std;

int main()
{
    int number;

    cout << "输入一个整数: ";
    cin >> number;

    cout << "输入的数字为: " << number;
    return ;
}
C++ 实例 - 实现两个数相加
#include <iostream>
using namespace std;

int main()
{
    int firstNumber, secondNumber, sumOfTwoNumbers;

    cout << "输入两个整数: ";
    cin >> firstNumber >> secondNumber;

    // 相加
    sumOfTwoNumbers = firstNumber + secondNumber;

    // 输出
    cout << firstNumber << " + " <<  secondNumber << " = " << sumOfTwoNumbers;     

    return ;
}
C++ 实例 - 求商及余数
#include <iostream>
using namespace std;

int main()
{
    int divisor, dividend, quotient, remainder;

    cout << "输入被除数: ";
    cin >> dividend;

    cout << "输入除数: ";
    cin >> divisor;

    quotient = dividend / divisor;
    remainder = dividend % divisor;

    cout << "商 = " << quotient << endl;
    cout << "余数 = " << remainder;

    return ;
}
C++ 实例 - 查看 int, float, double 和 char 变量大小
#include <iostream>
using namespace std;

int main()
{
    cout << "char: " << sizeof(char) << " 字节" << endl;
    cout << "int: " << sizeof(int) << " 字节" << endl;
    cout << "float: " << sizeof(float) << " 字节" << endl;
    cout << "double: " << sizeof(double) << " 字节" << endl;

    return ;
}
C++ 实例 - 交换两个数
#include <iostream>
using namespace std;

int main()
{
    int a = , b = , temp;

    cout << "交换之前：" << endl;
    cout << "a = " << a << ", b = " << b << endl;

    temp = a;
    a = b;
    b = temp;

    cout << "\n交换之后：" << endl;
    cout << "a = " << a << ", b = " << b << endl;

    return ;
}
C++ 实例 - 判断一个数是奇数还是偶数
#include <iostream>
using namespace std;

int main()
{
    int n;

    cout << "输入一个整数: ";
    cin >> n;

    if ( n %  == )
        cout << n << " 为偶数。";
    else
        cout << n << " 为奇数。";

    return ;
}
C++ 实例 - 判断元音/辅音
#include <iostream>
using namespace std;

int main()
{
    char c;
    int isLowercaseVowel, isUppercaseVowel;

    cout << "输入一个字母: ";
    cin >> c;

    // 小写字母元音
    isLowercaseVowel = (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');

    // 大写字母元音
    isUppercaseVowel = (c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U');

    // if 语句判断
    if (isLowercaseVowel || isUppercaseVowel)
        cout << c << " 是元音";
    else
        cout << c << " 是辅音";

    return ;
}
C++ 实例 - 判断三个数中的最大数
#include <iostream>
using namespace std;

int main()
{
    float n1, n2, n3;

    cout << "请输入三个数: ";
    cin >> n1 >> n2 >> n3;

    if(n1 >= n2 && n1 >= n3)
    {
        cout << "最大数为: " << n1;
    }

    if(n2 >= n1 && n2 >= n3)
    {
        cout << "最大数为: " << n2;
    }

    if(n3 >= n1 && n3 >= n2) {
        cout << "最大数为: " << n3;
    }

    return ;
}
C++ 实例 - 求一元二次方程的根
#include <iostream>
#include <cmath>
using namespace std;

int main() {

    float a, b, c, x1, x2, discriminant, realPart, imaginaryPart;
    cout << "输入 a, b 和 c: ";
    cin >> a >> b >> c;
    discriminant = b*b - *a*c;

    if (discriminant > ) {
        x1 = (-b + sqrt(discriminant)) / (*a);
        x2 = (-b - sqrt(discriminant)) / (*a);
        cout << "Roots are real and different." << endl;
        cout << "x1 = " << x1 << endl;
        cout << "x2 = " << x2 << endl;
    }

    else if (discriminant == ) {
        cout << "实根相同：" << endl;
        x1 = (-b + sqrt(discriminant)) / (*a);
        cout << "x1 = x2 =" << x1 << endl;
    }

    else {
        realPart = -b/(*a);
        imaginaryPart =sqrt(-discriminant)/(*a);
        cout << "实根不同："  << endl;
        cout << "x1 = " << realPart << "+" << imaginaryPart << "i" << endl;
        cout << "x2 = " << realPart << "-" << imaginaryPart << "i" << endl;
    }

    return ;
}
C++ 实例 - 计算自然数之和
#include <iostream>
using namespace std;

int main()
{
    int n, sum = ;

    cout << "输入一个正整数: ";
    cin >> n;

    for (int i = ; i <= n; ++i) {
        sum += i;
    }

    cout << "Sum = " << sum;
    return ;
}
C++ 实例 - 判断闰年
#include <iostream>
using namespace std;

int main()
{
    int year;

    cout << "输入年份: ";
    cin >> year;

    if (year %  == )
    {
        if (year %  == )
        {
            // // 这里如果被 400 整数是闰年
            if (year %  == )
                cout << year << " 是闰年";
            else
                cout << year << " 不是闰年";
        }
        else
            cout << year << " 是闰年";
    }
    else
        cout << year << " 不是闰年";

    return ;
}
C++ 实例 - 求一个数的阶乘
#include <iostream>
using namespace std;

int main()
{
    unsigned int n;
    unsigned long long factorial = ;

    cout << "输入一个整数: ";
    cin >> n;

    for(int i = ; i <=n; ++i)
    {
        factorial *= i;
    }

    cout << n << " 的阶乘为："<< " = " << factorial;
    return ;
}
C++ 实例 - 创建各类三角形图案
#include <iostream>
using namespace std;

int main()
{
    int rows;

    cout << "输入行数: ";
    cin >> rows;

    for(int i = ; i <= rows; ++i)
    {
        for(int j = ; j <= i; ++j)
        {
            cout << "* ";
        }
        cout << "\n";
    }
    return ;
}
#include <iostream>
using namespace std;

int main()
{
    char input, alphabet = 'A';

    cout << "输入最后一个大写字母: ";
    cin >> input;

    for(int i = ; i <= (input-'A'+); ++i)
    {
        for(int j = ; j <= i; ++j)
        {
            cout << alphabet << " ";
        }
        ++alphabet;

        cout << endl;
    }
    return ;
}
#include <iostream>
using namespace std;

int main()
{
    int rows;

    cout << "输入行数: ";
    cin >> rows;

    for(int i = rows; i >= ; --i)
    {
        for(int j = ; j <= i; ++j)
        {
            cout << "* ";
        }
        cout << endl;
    }

    return ;
}
#include <iostream>
using namespace std;

int main()
{
    int rows;

    cout << "输入行数: ";
    cin >> rows;

    for(int i = rows; i >= ; --i)
    {
        for(int j = ; j <= i; ++j)
        {
            cout << j << " ";
        }
        cout << endl;
    }

    return ;
}
#include <iostream>
using namespace std;

int main()
{
    int space, rows;

    cout <<"输入行数: ";
    cin >> rows;

    for(int i = , k = ; i <= rows; ++i, k = )
    {
        for(space = ; space <= rows-i; ++space)
        {
            cout <<"  ";
        }

        while(k != *i-)
        {
            cout << "* ";
            ++k;
        }
        cout << endl;
    }
    return ;
}
#include <iostream>
using namespace std;

int main()
{
    int rows, count = , count1 = , k = ;

    cout << "输入行数: ";
    cin >> rows;

    for(int i = ; i <= rows; ++i)
    {
        for(int space = ; space <= rows-i; ++space)
        {
            cout << "  ";
            ++count;
        }

        while(k != *i-)
        {
            if (count <= rows-)
            {
                cout << i+k << " ";
                ++count;
            }
            else
            {
                ++count1;
                cout << i+k-*count1 << " ";
            }
            ++k;
        }
        count1 = count = k = ;

        cout << endl;
    }
    return ;
}
#include <iostream>
using namespace std;

int main()
{
    int rows;

    cout << "输入行数: ";
    cin >> rows;

    for(int i = rows; i >= ; --i)
    {
        for(int space = ; space < rows-i; ++space)
            cout << "  ";

        for(int j = i; j <= *i-; ++j)
            cout << "* ";

        for(int j = ; j < i-; ++j)
            cout << "* ";

        cout << endl;
    }

    return ;
}
#include <iostream>
using namespace std;

int main()
{
    int rows, coef = ;

    cout << "Enter number of rows: ";
    cin >> rows;

    for(int i = ; i < rows; i++)
    {
        for(int space = ; space <= rows-i; space++)
            cout <<"  ";

        for(int j = ; j <= i; j++)
        {
            if (j ==  || i == )
                coef = ;
            else
                coef = coef*(i-j+)/j;

            cout << coef << "   ";
        }
        cout << endl;
    }

    return ;
}
#include <iostream>
using namespace std;

int main()
{
    int rows, number = ;

    cout << "输入行数: ";
    cin >> rows;

    for(int i = ; i <= rows; i++)
    {
        for(int j = ; j <= i; ++j)
        {
            cout << number << " ";
            ++number;
        }

        cout << endl;
    }

    return ;
}
C++ 实例 - 求两数的最大公约数
#include <iostream>
using namespace std;

int main()
{
    int n1, n2;

    cout << "输入两个整数: ";
    cin >> n1 >> n2;

    while(n1 != n2)
    {
        if(n1 > n2)
            n1 -= n2;
        else
            n2 -= n1;
    }

    cout << "HCF = " << n1;
    return ;
}
C++ 实例 - 求两数最小公倍数
#include <iostream>
using namespace std;

int main()
{
    int n1, n2, max;

    cout << "输入两个数: ";
    cin >> n1 >> n2;

    // 获取最大的数
    max = (n1 > n2) ? n1 : n2;

    do
    {
        if (max % n1 ==  && max % n2 == )
        {
            cout << "LCM = " << max;
            break;
        }
        else
            ++max;
    } while (true);

    return ;
}
C++ 实例 - 实现一个简单的计算器
#include <iostream>
using namespace std;

int main()
{
    char op;
    float num1, num2;

    cout << "输入运算符：+、-、*、/ : ";
    cin >> op;

    cout << "输入两个数: ";
    cin >> num1 >> num2;

    switch(op)
    {
        case '+':
            cout << num1+num2;
            break;

        case '-':
            cout << num1-num2;
            break;

        case '*':
            cout << num1*num2;
            break;

        case '/':
            cout << num1/num2;
            break;

        default:
            // 如果运算符不是 +, -, * 或 /, 提示错误信息
            cout << "Error!  请输入正确运算符。";
            break;
    }

    return ;
}
猴子吃桃问题
一只小猴子一天摘了许多桃子，第一天吃了一半，然后忍不住又吃了一个；第二天又吃了一半，再加上一个；后面每天都是这样吃。到第10天的时候，小猴子发现只有一个桃子了。问小猴子第一天共摘了多少个桃子。
#include <iostream>
using namespace std;
int main()
{
    int x, y, n;
    for (x=, n=; n<; y=(x+)*, x=y, n++);
        cout<<"第一天共摘的桃子数量为 "<<x<<endl;
    return ;
}