c++ primer plus 习题答案(2)

p221.8

 #include<iostream>
 #include<cstdlib>
 #include<cstring>
 using namespace std;
 const int SLEN = ;
 struct student{
     char fullname[SLEN];
     char hobby[SLEN];
     int ooplevel;
 };
 int getinfo(student pa[], int n);
 void display1(student st);
 void display2(const student *ps);
 void display3(const student pa[], int n);
 
 int main(){
     cout << "enter class size:";
     int class_size;
     cin >> class_size;
     while (cin.get() != '\n')
         continue;
     student *ptr_stu = new student[class_size];
     int entered = getinfo(ptr_stu, class_size);
     for (int i = ; i < entered; i++){
         display1(ptr_stu[i]);
         display2(&ptr_stu[i]);
     }
     display3(ptr_stu, entered);
     delete[]ptr_stu;
     cout << "done\n";
     system("pause");
     return ;
 }
 
 int getinfo(student pa[], int n){
     int i = , count = ;
     while (i < n && *pa[i].fullname != '\0'){
         cin.getline(pa[i].fullname, SLEN);
         cin.getline(pa[i].hobby, SLEN);
         cin >> pa[i].ooplevel;
         cin.get();
         count++;
         i++;
     }
     return count;
 }
 
 void display1(student st){
     cout << "st.fullname" << st.fullname <<
         endl << "st.hobby" << st.hobby <<
         endl << "st.ooplevel" << st.ooplevel <<
         endl;
 }
 
 void display2(const student *ps){
     cout << "ps->fullname" << ps->fullname <<
         endl << "ps->hobby" << ps->hobby <<
         endl << "ps->ooplevel" << ps->ooplevel <<
         endl;
 }
 
 void display3(const student pa[], int n){
     for (int i = ; i < n; i++){
         cout << "pa[i].fullname" << pa[i].fullname
             << endl << "pa[i].hobby" << pa[i].hobby
             << endl << "pa[i].ooplevel" << pa[i].ooplevel
             << endl;
     }
 }

p259.2

 #include<iostream>
 #include<cstdlib>
 #include<cstring>
 using namespace std;
 struct candybar {
     char brand[];
     float weight;
     int calory;
 };
 void assign(candybar &, char br[]="millennium munch", float w=2.85, int c=);
 void show_menu(candybar&);
 
 int main(){
     candybar tasty;
     assign(tasty);
     show_menu(tasty);
     system("pause");
     return ;
 }
 
 void assign(candybar &delicious, char br[], float w , int c){
     strcpy(delicious.brand, br);
     delicious.weight = w;
     delicious.calory = c;
 }
 
 void show_menu(candybar&delicious){
     cout << delicious.brand << endl;
     cout << delicious.weight << endl;
     cout << delicious.calory << endl;
 }

p259.4

 #include<iostream>
 #include<cstdlib>
 #include<cctype>
 using namespace std;
 struct stringy{
     char* str;
     int ct;
 };
 void set(stringy &, const char*);
 void show(const stringy &, int times = );
 void show(const char*, int times = );
 
 int main(){
     stringy beany;
     char testing[] = "reality isn't what it used to be.";
     set(beany, testing);
     show(beany);
     show(beany, );
     delete beany.str;
     testing[] = 'D';
     testing[] = 'u';
     show(testing);
     show(testing, );
     show("Done!");
     system("pause");
     return ;
 }
 
 void set(stringy &beany, const char* testing){
     int num = strlen(testing);
     beany.str = new char[num + ];
     strcpy(beany.str, testing);
     beany.ct = num;
 }
 
 void show(const stringy &beany, int times){
     for (int i = ; i < times; i++)
         cout << beany.str << endl
             << beany.ct << endl;
 }
 
 void show(const char* testing, int times){
     for (int i = ; i < times; i++)
         cout << testing << endl;
 }

p260.6

 #include<iostream>
 #include<cstdlib>
 #include<cstring>
 using namespace std;
 template<class T>
 T maxn(T ar[], int num);
 template<> char *maxn(char *pt[], int num);
 
 int main(){
     int num1[];
     double num2[];
     cout << "enter the member of two array\n";
     for (int i = ; i < ; i++)
         cin >> num1[i];
     for (int i = ; i < ; i++)
         cin >> num2[i];
     int imax = maxn(num1, );
     double dmax = maxn(num2, );
     cout << "imax is" << imax << endl
         << "dmax is" << dmax << endl;
     char *str[];
     str[] = "his eyes came round";
     str[] = "it all seems very unchanged";
     str[] = "which contain of old the pipes";
     str[] = "yes, billy, i know";
     str[] = "will you be please to dine";
     char *address = maxn(str, );
     cout << (int*)address << " " <<
         address << endl;
     system("pause");
     return ;
 }
 
 template<class T>
 T maxn(T ar[], int num){
     T max=ar[];
     for (int i = ; i < num; i++)
         if (max < ar[i])
             max = ar[i];
     return max;
 }
 
 template<> char *maxn(char *pt[], int num){
     int length[], i;
     for (i = ; i < ; i++)
         length[i] = strlen(pt[i]);
     int max = length[];
     for (i = ; i < ; i++)
         if (max < length[i])
             max = length[i];
     for (i = ; i < ; i++)
         if (max == length[i])
             break;
     return pt[i];
 }