STL之priority_queue为复合结构排序

priority_queue为复合结构排序：　

 #include <iostream>

 #include <queue>

 using namespace std;

 struct Node{

     int x;

     string  y;

     Node( int a= , string b = "" ):

         x(a), y(b) {}

 };

 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！

                                     // bool为真的 优先级小

     if( a.x == b.x ) return a.y < b.y;

     return a.x < b.x;

 }

       //自定义重载小于操作符

 int main(){

    /********************************************

    对于自定义类型，则必须自己重载 operator<

    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。

    看下面的例子

    *******************************************/

     cout<<"自定义： "<<endl;

     priority_queue<Node> q2;

     priority_queue<int> q3;

     std::string tmp = "";

     for( int i= ; i>; --i ){

         tmp = tmp + "";

         q2.push( Node(i, tmp) );

         q3.push(i);

     }

     while( !q2.empty() ){

         cout << q2.top().x << ' ' << q2.top().y << endl;

         q2.pop();

     }

     while( !q3.empty() ){

         cout << "q3 output: "<<q3.top() << endl;

         q3.pop();

     }

     //注意上面不能这样来定义：priority_queue<Node, vector<Node>, greater<Node> >;

     //这样定义是错误的！！！！

     //原因是：greater<node>没有定义

     //必须定义如下函数对象，才能这样定义：

     // priority_queue<Node, vector<Node>, cmp >;

     /*

     struct cmp{

     bool operator() ( Node a, Node b ){

         if( a.x== b.x ) return a.y> b.y;

         return a.x> b.x; }

     };

    */

     return ;

 }

 root@u18:~/cp/test# g++ priority.cpp  -g -Wall

 root@u18:~/cp/test# valgrind  --tool=memcheck --leak-check=yes ./a.out

 ==== Memcheck, a memory error detector

 ==== Copyright (C) -, and GNU GPL'd, by Julian Seward et al.

 ==== Using Valgrind-3.7. and LibVEX; rerun with -h for copyright info

 ==== Command: ./a.out

 ====

 自定义：

 q3 output:

 q3 output:

 q3 output:

 q3 output:

 q3 output:

 q3 output:

 q3 output:

 q3 output:

 q3 output:

 q3 output:

 ====

 ==== HEAP SUMMARY:

 ====     in use at exit:  bytes in  blocks

 ====   total heap usage:  allocs,  frees, , bytes allocated

 ====

 ==== All heap blocks were freed -- no leaks are possible

 ====

 ==== For counts of detected and suppressed errors, rerun with: -v

 ==== ERROR SUMMARY:  errors from  contexts (suppressed:  from )