1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
|
#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
Pss("Hampson", "Godalming"),
Pss("Moran", "Eugene"),
Pss("Goldberg", "Eugene"),
Pss("Moran", "Godalming"),
Pss("Goldberg", "Chicago"),
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
*/
|
