STL之priority_queue为复合结构排序

priority_queue为复合结构排序：　

 1 #include <iostream>
 2 #include <queue>
 3
 4 using namespace std;
 5 struct Node{
 6     int x;
 7     string  y;
 8     Node( int a= 0, string b = "" ):
 9         x(a), y(b) {}
10 };
11 bool operator<( Node a, Node b ){   // 注意这里的顺序和sort()里面的谓词函数不一样！
12                                     // bool为真的 优先级小
13     if( a.x == b.x ) return a.y < b.y;
14     return a.x < b.x;
15 }
16       //自定义重载小于操作符
17 int main(){
18    /********************************************
19    对于自定义类型，则必须自己重载 operator<
20    自定义类型重载 operator< 后，声明对象时就可以只带一个模板参数。
21    看下面的例子
22    *******************************************/
23
24     cout<<"自定义： "<<endl;
25     priority_queue<Node> q2;
26     priority_queue<int> q3;
27     std::string tmp = "";
28
29     for( int i= 10; i>0; --i ){
30         tmp = tmp + "12";
31         q2.push( Node(i, tmp) );
32         q3.push(i);
33     }
34     while( !q2.empty() ){
35         cout << q2.top().x << ‘ ‘ << q2.top().y << endl;
36         q2.pop();
37     }
38     while( !q3.empty() ){
39         cout << "q3 output: "<<q3.top() << endl;
40         q3.pop();
41     }
42     //注意上面不能这样来定义：priority_queue<Node, vector<Node>, greater<Node> >;
43     //这样定义是错误的！！！！
44     //原因是：greater<node>没有定义
45
46     //必须定义如下函数对象，才能这样定义：
47     // priority_queue<Node, vector<Node>, cmp >;
48     /*
49     struct cmp{
50     bool operator() ( Node a, Node b ){
51         if( a.x== b.x ) return a.y> b.y;
52
53         return a.x> b.x; }
54     };
55    */
56     return 0;
57 }
58
59 [email protected]:~/cp/test# g++ priority.cpp  -g -Wall
60 [email protected]:~/cp/test# valgrind  --tool=memcheck --leak-check=yes ./a.out
61 ==24385== Memcheck, a memory error detector
62 ==24385== Copyright (C) 2002-2011, and GNU GPL‘d, by Julian Seward et al.
63 ==24385== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
64 ==24385== Command: ./a.out
65 ==24385==
66 自定义：
67 10 12
68 9 1212
69 8 121212
70 7 12121212
71 6 1212121212
72 5 121212121212
73 4 12121212121212
74 3 1212121212121212
75 2 121212121212121212
76 1 12121212121212121212
77 q3 output: 10
78 q3 output: 9
79 q3 output: 8
80 q3 output: 7
81 q3 output: 6
82 q3 output: 5
83 q3 output: 4
84 q3 output: 3
85 q3 output: 2
86 q3 output: 1
87 ==24385==
88 ==24385== HEAP SUMMARY:
89 ==24385==     in use at exit: 0 bytes in 0 blocks
90 ==24385==   total heap usage: 20 allocs, 20 frees, 1,012 bytes allocated
91 ==24385==
92 ==24385== All heap blocks were freed -- no leaks are possible
93 ==24385==
94 ==24385== For counts of detected and suppressed errors, rerun with: -v
95 ==24385== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2)