C++ Primer（第5版） 练习 10.17

练习 10.17 重写10.3.1节练习10.12（第345页）的程序，在对sort的调用中使用lambda来代替函数compareIsbn。

环境：Linux Ubuntu（云服务器）

工具：vim

代码块

/*************************************************************************
	> File Name: ex10.17.cpp
	> Author: 
	> Mail: 
	> Created Time: Sat 02 Mar 2024 08:11:38 PM CST
 ************************************************************************/

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

struct Sales_data{
    Sales_data(const string &s, unsigned n, double p):
                bookNo(s), units_sold(n), price(p), revenue(p * n) {}
    Sales_data(): Sales_data("", 0, 0) {}
    Sales_data(string s): Sales_data(s, 0, 0) {}
    Sales_data(istream &);

    friend ostream &print(ostream&, const Sales_data&);
    friend istream &read(istream&, Sales_data&);

    string isbn() const;
    Sales_data& combine(const Sales_data&);
    double avg_price() const;

    string bookNo;
    unsigned units_sold = 0;
    double price = 0.0;
    double revenue = 0.0;
};

Sales_data::Sales_data(istream &in){
    read(in, *this);
}

string Sales_data::isbn() const{
    return this->bookNo;
}

Sales_data& Sales_data::combine(const Sales_data &rhs){
    units_sold += rhs.units_sold;
    revenue += rhs.revenue;
    return *this;
}

double Sales_data::avg_price() const{
    if(units_sold){
        return revenue / units_sold;
    }
    else{
        return 0;
    }
}

Sales_data add(const Sales_data &sd1, const Sales_data &sd2){
    Sales_data t = sd1;
    t.combine(sd2);
    return t;
}

ostream &print(ostream &output, const Sales_data &sd){
    output<<sd.bookNo<<" "<<sd.units_sold<<" "<<sd.price<<" "<<sd.revenue<<" "<<sd.avg_price()<<endl;
    return output;
}

istream &read(istream &input, Sales_data &sd){
    input>>sd.bookNo>>sd.units_sold>>sd.price;
    sd.revenue = sd.price * sd.units_sold;
    return input;
}

bool compareIsbn(const Sales_data &s1, const Sales_data &s2){
    return s1.isbn() < s2.isbn();
}

int main(){
    vector<Sales_data> sales;
    Sales_data temp;
   
    cout<<"Enter sales data: "<<endl;
    while(read(cin, temp)){
        sales.push_back(temp);
    }
    cout<<endl;

    cout<<"Original sales data: "<<endl;
    for(const auto s : sales){
        print(cout, s);
    }
    cout<<endl;

    stable_sort(sales.begin(), sales.end(), [](const Sales_data &s1, const Sales_data &s2){ return s1.isbn() < s2.isbn(); });

    cout<<"New sort: "<<endl;
    for(const auto s : sales){
        print(cout, s);
    }
    cout<<endl;

    return 0;
}

运行结果显示如下