第一章~编程练习解答

第一章的友好度还是相当滴
习题解答

1.2习题

1.2认为最大的收获：

注意

// Exercise 1.3 Output Hello, World。
#include<iostream>
int main(){
    std::cout<< "Hello，World。" << std::endl;
    return 0;
}
 
// Exercise 1.4 Input two numbers by using the char of "*" to print product
#include<iostream>
int main(){
    int v1 = 0, v2 = 0;
    std::cin >> v1 >> v2;
    std::cout << v1 * v2 << std::endl;
    return 0;
}

// 将样例输出语句分离单个语句中 
// std::out<<"The sum of: "<<v1 + v2<<" end!"<<std::endl
#include<iostream>
int main(){
    int v1 = 5, v2 = 3;
    std::cout << "The sum of: ";
    std::cout << v1 + v2;
    std::cout << " end!";
    std::cout << std::endl;
    return 0;
}

1.4习题~(循环与不定量数据读入)

// use "while" sum 50 + 51 + 52 .... + 100 print reult
#include<iostream>
int main(){
    int val = 50, sum = 0;
    while(val <= 100){
        sum += val;
        val++;
    }
    std::cout << sum;
    return 0;
}

// use "while" print 10 9 8 ... 0
#include<iostream>
int main(){
    int val = 10;
    while(val >= 0){
        std::cout << val << " ";
        val--;
    }
    std::cout << std::endl; 
    return 0;
}

// 编写程序输入两个整数 打印这两个整数范围内的所有整数 
#include<iostream>
int main(){
    int left = 0, right = 0;
    std::cin >> left >> right;
    std::cout << "[left, right] includes: ";
    while(left <= right){
        std::cout << left << " ";
        left++;
    }
    std::cout << std::endl;
    return 0;
} 

 // use "for" sum of 50~100 
 #include<iostream>
 int main(){
    int sum = 0;
    for(int i = 50; i <= 100; i++){
        sum += i; 
    }
    std::cout << "Sum of : " << sum << std::endl; 
    return 0;
 }

// print 10 to 0 use "for" and "--"
#include<iostream>
int main(){
    for(int i = 10; i >= 0; --i){
        std::cout << i << " ";
    }
    std::cout << std::endl;
    return 0;
} 

// input two numbers [a, b] print a to b all numbers
#include<iostream>
int main(){
    int a = 0, b = 0;
    std::cin >> a >> b;
    for(int i = a; i <= b; i++){
        std::cout << i << " ";
    }
    std::cout << std::endl;
    return 0;
}

// 从cin 读取一组数 求和 不定量数据
#include<iostream>
int main(){
    int val = 0, sum = 0;
    while(std::cin >> val){
        sum += val;
    }
    std::cout << "sum of " << sum << std::endl;
    return 0;
} 

最后~简单的C++项目 书店程序

收获：类的初次了解，c++项目的创建与操作 以下要点(附书中头文件源码)

注意

由于项目的设计，以下将练习封装为函数以便区分

#include"Sales_item.h"
void readAndPrint();
void testAdd();
void sumOfSales();
void staSales();
void completeRoutine();

int main(void) {
    //readAndPrint();
    //testAdd();
    //sumOfSales();
    //staSales();
    completeRoutine();
    return 0;
}

// p20 1.5.1_1 读取一组图书销售记录 并且将记录打印在标准输出
void readAndPrint(){
    Sales_item book;
    std::cin >> book;
    std::cout << book << std::endl; 
}

// 1.5.1_2 读取两个ISBN(书号)相同的Sales_item 对象, 输出和
void testAdd(){
    Sales_item item1, item2;
    std::cout << "输入两个相同ISBN的书籍信息 (书号 售出本数 单价)" << std::endl;
    std::cin >> item1 >> item2;
    std::cout << item1 + item2 << std::endl;
}

// 1.5.1_3 读取具有多个连续相同ISBN的记录 输出所有相同记录的和
void sumOfSales(){
    std::cout << "输入多个相同ISBN的书籍信息 (书号 售出本数 单价)" << std::endl;
    Sales_item item, sum;
    while(std::cin >> item){// ctrl+z 录入结束 
        sum += item;
    }
    std::cout << "sum of " << sum << std::endl;
    
}

// p21 1.5.2_1 读取多条销售记录 并统计每个ISBN(即每本书)有几条记录
void staSales(){
    std::cout << "输入多条书籍销售记录 (书号 售出本数 单价)" << std::endl;
    Sales_item curItem, nextItem;
    if(std::cin >> curItem){
        int cnt = 1; // 记录条数
        while(std::cin >> nextItem){
            if(nextItem.isbn == curItem.isbn){
                cnt++;
            }else{
                std::cout << curItem.isbn << " has saled " << cnt << " books"<<std::endl; 
                curItem = nextItem;
                cnt = 1; // 初始化计数 
            }
        }
        // 打印最后一条记录 
        std::cout << curItem.isbn << " has saled " << cnt << " books"<<std::endl;  
    }
}
    
// 书店程序 
// 假定读入的销售记录书号相同的已经聚在一起 输出每本书的最终销售记录
void completeRoutine(){
    std::cout << "输入多条书籍销售记录 (书号 售出本数 单价)" << std::endl;
    Sales_item curItem, nextItem;
    if(std::cin >> curItem){
        while(std::cin >> nextItem){
            if(nextItem.isbn == curItem.isbn){
                curItem += nextItem;// 销售信息累加 
            }else{
                std::cout << "销售记录：" << curItem << std::endl;
                curItem = nextItem;// 更新为下一本数的销售情况 
            }
        }
        // 最后一本书的记录 
        std::cout << "销售记录：" << curItem << std::endl;
        
    }else{
        std::cout << "无效的书籍信息!" << std::endl;
    }
    
} 

以上引用头文件源码

#ifndef SALESITEM_H
#define SALESITEM_H
#include <iostream>
#include <string>

class Sales_item{
public:
    Sales_item(const std::string &book):isbn(book),units_sold(0),revenue(0.0){}
    Sales_item(std::istream &is){ is >> *this;}
    friend std::istream& operator>>(std::istream &,Sales_item &);
    friend std::ostream& operator<<(std::ostream &,const Sales_item &);
public:
    Sales_item & operator+=(const Sales_item&);
public:
    double avg_price() const;
    bool same_isbn(const Sales_item &rhs)const{
    return isbn == rhs.isbn;
    }
    Sales_item():units_sold(0),revenue(0.0){}
public:
    std::string isbn;
    unsigned units_sold;
    double revenue;
};

using std::istream;
using std::ostream;
Sales_item operator+(const Sales_item &,const Sales_item &);

inline bool operator==(const Sales_item &lhs,const Sales_item &rhs){
    return lhs.units_sold == rhs.units_sold && lhs.revenue == rhs.revenue && lhs.same_isbn(rhs);
}

inline bool operator!=(const Sales_item &lhs,const Sales_item &rhs){
    return !(lhs == rhs);
}

inline Sales_item & Sales_item::operator +=(const Sales_item &rhs){
    units_sold += rhs.units_sold;
    revenue += rhs.revenue;
    return *this;
}

inline Sales_item operator+(const Sales_item &lhs,const Sales_item &rhs){
    Sales_item ret(lhs);
    ret += rhs;
    return ret;
}

inline istream& operator>>(istream &in,Sales_item &s){
    double price;
    in >> s.isbn >> s.units_sold >> price;
    if(in)
        s.revenue = s.units_sold * price;
    else
        s = Sales_item();
    return in;
}

inline ostream& operator<<(ostream &out,const Sales_item &s){
    out << s.isbn << "\t" <<s.units_sold << "\t" << s.revenue << "\t" << s.avg_price();
    return out;
}

inline double Sales_item::avg_price() const{
    if(units_sold)
        return revenue/units_sold;
    else
        return 0;
}
#endif