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 )