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];

 }