使用tuple返回多个值

17.4编写并测试findbook函数

#include<iostream>
#include<vector>
#include<string>
#include<tuple>
#include<algorithm>
#include"Sales_data.h"
using namespace std;
typedef tuple<vector<Sales_data>::size_type,vector<Sales_data>::const_iterator,vector<Sales_data>::const_iterator> matches;

vector<matches> findbook(const vector<vector<Sales_data>> &files,const string &book)
{
    vector<matches> ret;
    for(auto it=files.begin();it!=files.end();++it)
    {
        auto found=equal_range(it->begin(),it->end(),book,compareIsbn);
        if(found.first!=found.second)
            ret.push_back(make_tuple(it-files.begin(),found.first,found.second));
    }
    return ret;
}

void reportResult(istream &in,ostream &os,const vector<vector<Sales_data>> &files)
{
    string s;
    while(in>>s)
    {
        auto trans=findbook(files,s);
        if(trans.empty())
        {
            cout<<s<<" not found in any stores "<<endl;
            continue;
        }
        for(const auto &store:trans)
        {
            os<<"stores "<<get<>(store)<<" sales: "
                <<accumulate(get<>(store),get<>(store),Sales_data(s))
                <<endl;
        }
    }
}

int main()
{

}

17.5重写findbook，令其返回一个pair，包含一个索引和一个迭代器pair。

typedef pair<vector<Sales_data>::size_type,pair<vector<Sales_data>::const_iterator,vector<Sales_data>::const_iterator>> match;
vector<match> findbook1(const vector<vector<Sales_data>> &files,const string &book)
{
    vector<match> ret;
    for(auto it=files.begin();it!=files.end();++it)
    {
        auto found=equal_range(it->begin(),it->end(),book,compareIsbn);
        if(found.first!=found.second)
            ret.push_back(make_pair(it-files.begin(),make_pair(found.first,found.second)));
    }
    return ret;
}