priority_queue

特性：最大值（或者二元谓词认为是最大值）的元素位于队首，只允许在队首进行操作。迭代器类型为：随机访问迭代器。默认底层容器为：vector，可以使用deque，具体函数如下：

1.        构造器：

示例程序：

// constructing priority queues

#include <iostream>       // std::cout

#include <queue>          // std::priority_queue

#include <vector>         // std::vector

#include <functional>     // std::greater

 

class mycomparison

{

   bool reverse;

public:

   mycomparison(const bool& revparam=false)

    {

       reverse=revparam;

    }

   bool operator() (const int& lhs, const int&rhs) const

    {

       if (reverse) return (lhs>rhs);

       else return (lhs<rhs);

    }

};

 

int main ()

{

   int myints[]= {10,60,50,20};

 

   std::priority_queue<int> first;

   std::priority_queue<int> second (myints,myints+4);

   std::priority_queue<int, std::vector<int>,std::greater<int> >

   third (myints,myints+4);

   // using mycomparison:

   typedefstd::priority_queue<int,std::vector<int>,mycomparison> mypq_type;

 

   mypq_type fourth;                      // less-than comparison

   mypq_type fifth (mycomparison(true));  // greater-than comparison

 

   return 0;

}

解析：

The example does not produce any output,but it constructs different priority_queueobjects:
- First is empty.
- Second contains the four ints defined for myints, with 60 (the highest) atits top.
- Third has the same four ints, but because it uses greater instead of the default(which is less), it has 10 as itstop element.
- Fourth and fifth are very similar to first: they are both empty, except thatthese use mycomparison for comparisons, which is a special stateful comparisonfunction that behaves differently depending on a flag set on construction.

2.        判断优先队列是否为空：bool B=mypq.empty()

3.        返回优先队列中元素的个数：mypq.size();

4.        返回优先队列中最开头元素的引用：mypq.top()

5.        向优先队列中插入元素：mypq.push(elementvalue)；

6.        删除优先队列最开头的元素：mypq.pop()

示例程序：

#include<iostream>

#include<queue>

using namespace std;

int main()

{

   priority_queue <int> pq;

   cout<<pq.empty()<<endl;

   cout<<pq.size()<<endl;

   for(int i=0;i<=5;i++)

    {

       pq.push(i);

    }

   cout<<pq.size()<<endl;

   while(!pq.empty())

    {

       cout<<"The top element is:"<<pq.top()<<endl;

       pq.pop();

    }

   return 0;

}

运行结果：

1

0

6

The top element is:5

The top element is:4

The top element is:3

The top element is:2

The top element is:1

The top element is:0