c++ primer 练习 2.39、2.40、2.41、2.42

来源：互联网发布：中国航空制造业知乎编辑：程序博客网时间：2024/05/18 17:59

很久以前做的，前面的练习比较应付、有些地方不太靠谱，但是后面更新的会越来越认真！

2.39

prog1.cpp:1:12: error: expected ';' after struct definition struct Foo{}

2.40

struct Sales_data{    std::string bookNo;    unsigned units_sold = 0;    double price = 0.0;    double revenue = 0.0;};

2.41

#include<iostream>#include<string>struct Sales_data{    std::string bookNo;    unsigned units_sold = 0;    double price = 0.0;    double revenue = 0.0;};int main(){    Sales_data data;    // std::cin >> data;    std::cin >> data.bookNo >> data.units_sold >> data.price;    // std::cout << data;    std::cout << data.bookNo << " " << data.units_sold << " " << data.price << std::endl;    return 0;}

#include<iostream>#include<string>struct Sales_data{    std::string bookNo;    unsigned units_sold = 0;    double price = 0.0;    double revenue = 0.0;};int main(){    Sales_data data1, data2;    // std::cin >> data1 >> data2;    std::cin >> data1.bookNo >> data1.units_sold >> data1.price;    std::cin >> data2.bookNo >> data2.units_sold >> data2.price;    // std::cout << data1 + data2;    std::cout << data1.bookNo << " " << data1.units_sold + data2.units_sold << " " << data1.price << std::endl;    return 0;}

#include<iostream>#include<string>struct Sales_data{    std::string bookNo;    unsigned units_sold = 0;    double price = 0.0;    double revenue = 0.0;};int main(){    Sales_data data, sum_data;    while(std::cin >> data.bookNo >> data.units_sold >> data.price)        sum_data.units_sold += data.units_sold;    std::cout << data.bookNo << " " << sum_data.units_sold << " " << data.price << std::endl;    return 0;}

#include<iostream>#include<string>struct Sales_data{    std::string bookNo;    unsigned units_sold = 0;    double price = 0.0;    double revenue = 0.0;};int main(){    int num = 0;    std::string last_bookNo;    Sales_data temp_data;    // 读取第一个    // std::cin >> temp_data;    std::cin >> temp_data.bookNo >> temp_data.units_sold >> temp_data.price;    last_bookNo = temp_data.bookNo;    num = 1;    // while(std::cin >> temp_data){    while(std::cin >> temp_data.bookNo >> temp_data.units_sold >> temp_data.price){        if(temp_data.bookNo == last_bookNo){            ++num;        }        else{            std::cout << last_bookNo << " " << num;            last_bookNo = temp_data.bookNo;            num = 1;        }    }    std::cout << last_bookNo << " " << num;    return 0;}

#include<iostream>#include<string>struct Sales_data{    std::string bookNo;    unsigned units_sold = 0;    double price = 0.0;    double revenue = 0.0;};int main(){    Sales_data total;    if(std::cin >> total.bookNo >> total.units_sold >> total.price){        Sales_data trans;        // while(std::cin >> total)        while(std::cin >> trans.bookNo >> trans.units_sold >> trans.price){            if(total.bookNo == trans.bookNo){                total.units_sold += trans.units_sold;            }else{                // std::cout << total << std::endl;                std::cout << total.bookNo << " " << total.units_sold << " " << total.price << std::endl;                // total = trans;                total = trans;            }        }        std::cout << total.bookNo << " " << total.units_sold << " " << total.price << std::endl;    }else{        std::cerr << "No data?" << std::endl;        return -1;    }    return 0;}

2.42

略

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