c++ primer plus(第6版)中文版 第四章编程练习答案

第四章编程练习答案

4.1接收姓名，成绩等级和年龄，输出时成绩等级下调

//4.1接收姓名，成绩等级和年龄，输出时成绩等级下调#include <iostream>#include <string>using namespace std;int main () {     string Firstname,Lastname;cout << "What is your first name? ";getline(cin, Firstname);cout << "What is your last name? ";cin >> Lastname;charchgrade;cout << "What letter grade do you deserve? ";cin >> chgrade;unsignedint Age;cout << "What is your age? ";cin >> Age;cout << "Name: " << Lastname << "   " << Firstname << endl;cout << "Grade: " << char(chgrade + 1) << endl;cout << "Age: " << Age << endl;} 

4.2用c++ string类改写程序清单4.4

//4.2用c++ string类改写程序清单4.4#include <iostream>#include <string>using namespace std;int main () {     string Name;cout << "Enter your name: ";cin >> Name;string Dessert;cout << "Enter your favorite dessert: ";cin >> Dessert;cout << "I have some delicious " << Dessert;cout << " for you, " << Name << endl;} 

4.3输入名和姓，输出“名， 姓”（用cstring和char数组）

//4.3输入名和姓，输出“名， 姓”（用cstring和char数组）#include <iostream>#include <cstring>using namespace std;int main () { charfirstname[20],lastname[20],name[40];cout << "Enter your first name: ";cin.getline(firstname,20);cout << "Enter your last name: ";cin.getline(lastname, 20);strcpy(name, lastname);strcat(name, ", ");strcat(name, firstname);cout << "Here’s the information in a single string: " << name << endl;} 

4.4输入名和姓，输出“名， 姓”（用string类和函数）

//4.4输入名和姓，输出“名， 姓”（用string类和函数）#include <iostream>#include <string>using namespace std;int main () {     string firstname,lastname,name;cout << "Enter your first name: ";cin >> firstname;cout << "Enter your last name: ";cin >> lastname;name += firstname + ','  + lastname;cout << "Here’s the information in a single string: " << name << endl;} 

4.5建立结构体CandyBar，包括品牌，重量，卡路里3个成员，初始化并输出

//4.5建立结构体CandyBar，包括品牌，重量，卡路里3个成员，初始化并输出#include <iostream>#include <string>using namespace std;struct CandyBar{string name;doubleweight;doublecalories;};int main () {     CandyBarsnack = {"Mocha Munch", 2.3, 350};cout << snack.name << "\n" << snack.weight << "\n" << snack.calories << endl; } 

4.6结构体同题4.5，初始化为3个元素并输出

//4.6结构体同题4.5，初始化为3个元素并输出#include <iostream>#include <string>using namespace std;struct CandyBar{string name;doubleweight;doublecalories;};int main (void) {     CandyBarsnack[] ={{"A", 1, 10},{"B", 2, 20},{"C", 3, 30}};cout << snack[0].name << "\t" << snack[0].weight << "\t" << snack[0].calories << endl; cout << snack[1].name << "\t" << snack[1].weight << "\t" << snack[1].calories << endl; cout << snack[2].name << "\t" << snack[2].weight << "\t" << snack[2].calories << endl; } 

4.7Pizza有三个记录值（公司名称，直径，重量），主函数可输入可输出

//4.7Pizza有三个记录值（公司名称，直径，重量），主函数可输入可输出#include <iostream>#include <string>using namespace std;struct Pizza{string company_name;doublediameter;doubleweight;};int main () {     Pizzapizza;cout << "输入披萨名：";getline(cin, pizza.company_name);cout << "输入披萨直径（厘米）：";cin >> pizza.diameter;cout << "输入披萨重量（克）：";cin >> pizza.weight;cout << pizza.company_name << "公司出品直径为" << pizza.diameter << "厘米重量为" << pizza.weight << "克的披萨" << endl;} 

4.8对4.7的结构体用new来分配内存

//4.8对4.7的结构体用new来分配内存#include <iostream>#include <string>using namespace std;structPizza{stringcompany_name;doublediameter;doubleweight;};int main () {     Pizza*pizza = new Pizza;cout << "输入披萨直径（厘米）：";cin >> pizza->diameter;// 回车符仍保留在输入流中cin.get();  //取先前的回车符cout << "输入披萨名：";getline(cin, pizza->company_name);cout << "输入披萨重量（克）：";cin >> pizza->weight;cout << pizza->company_name << "公司出品直径为" << pizza->diameter << "厘米重量为" << pizza->weight << "克的披萨" << endl;delete pizza;pizza = NULL;} 

4.9对4.6使用new分配内存

//4.9对4.6使用new分配内存#include <iostream>#include <string>using namespace std;struct CandyBar{stringname;doubleweight;doublecalories;};int main () {     CandyBar* candybar_list = new CandyBar [3];candybar_list[0].name = "A";candybar_list[0].weight = 1;candybar_list[0].calories = 10;candybar_list[1].name = "B";candybar_list[1].weight = 2;candybar_list[1].calories = 20;candybar_list[2].name = "C";candybar_list[2].weight = 3;candybar_list[2].calories = 20;cout << candybar_list[0].name << "\t" << candybar_list[0].weight << "\t" << candybar_list[0].calories << endl; cout << candybar_list[1].name << "\t" << candybar_list[1].weight << "\t" << candybar_list[1].calories << endl; cout << candybar_list[2].name << "\t" << candybar_list[2].weight << "\t" << candybar_list[2].calories << endl; delete [] candybar_list;} 

4.10请用户输入3次成绩，显示次数和平均成绩

//4.10请用户输入3次成绩，显示次数和平均成绩(array为c++11新加标准，vector可通用)#include <iostream>//#include <vector>#include <array>using namespace std;int main () {//vector<double> dash(3);array<double,3> dash; for(int i=0;i<3;i++)       {  cout<<"Enter the "<<i+1<<" time :";          cin>>dash[i];     }  cout << "共计输入3次短跑成绩，平均分为" << (dash[0] + dash[1] + dash[2]) / 3 << endl;}