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#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <iterator>
using namespace std;
struct Pss: public pair<string, string> // 1
{
Pss(string const &s1, string const &s2)
:
pair<string, string>(s1, s2)
{}
};
ostream &operator<<(ostream &out, Pss const &p) // 2
{
return out << " " << p.first << " " << p.second << '\n';
}
class Sortby
{
string Pss::*d_field;
public:
Sortby(string Pss::*field) // 3
:
d_field(field)
{}
bool operator()(Pss const &p1, Pss const &p2) const // 4
{
return p1.*d_field < p2.*d_field;
}
};
int main()
{
vector<Pss> namecity; // 5
namecity.push_back(Pss("Hampson", "Godalming"));
namecity.push_back(Pss("Moran", "Eugene"));
namecity.push_back(Pss("Goldberg", "Eugene"));
namecity.push_back(Pss("Moran", "Godalming"));
namecity.push_back(Pss("Goldberg", "Chicago"));
namecity.push_back(Pss("Hampson", "Eugene"));
sort(namecity.begin(), namecity.end(), Sortby(&Pss::first)); // 6
cout << "sorted by names:\n";
copy(namecity.begin(), namecity.end(), ostream_iterator<Pss>(cout));
// 7
stable_sort(namecity.begin(), namecity.end(), Sortby(&Pss::second));
cout << "sorted by names within sorted cities:\n";
copy(namecity.begin(), namecity.end(), ostream_iterator<Pss>(cout));
}
/*
Displays:
sorted by names:
Goldberg Eugene
Goldberg Chicago
Hampson Godalming
Hampson Eugene
Moran Eugene
Moran Godalming
sorted by names within sorted cities:
Goldberg Chicago
Goldberg Eugene
Hampson Eugene
Moran Eugene
Hampson Godalming
Moran Godalming
*/
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