C++优先队列/priority_queue(最大堆、最小堆)

定义： priority_queue q;最大堆（默认为最大堆）
priority_queue q;最小堆
Priority queues are a type of container adaptors, specifically designed such that its first element is always the greatest of the elements it contains, according to some strict weak ordering criterion.

This context is similar to a heap, where elements can be inserted at any moment, and only the max heap element can be retrieved (the one at the top in the priority queue).

The underlying container（第二个参数） may be any of the standard container class templates or some other specifically designed container class. The container shall be accessible through random access iterators and support the following operations:

empty()
size()
front()
push_back()
pop_back()

参数：
第一个参数T：元素（element）类型
第二个参数Container：必须是容器类型Container，用来存储元素（element），其类型必须是第一个参数
第三个参数Compare：比较形式，默认是less

最大堆

#include 
#include 
#include 
using namespace std;
int main(){
    priority_queue<int,vector<int>,less<int> > big_heap;
    big_heap.push(2);
    big_heap.push(3);
    big_heap.push(5);
    big_heap.push(0);
    while(!big_heap.empty()){
        cout<<big_heap.top()<<endl;
        big_heap.pop();
        
    }
}

输出

5
3
2
0

最小堆

#include 
#include 
#include 
using namespace std;
int main(){
    priority_queue<int,vector<int>,greater<int> > small_heap;
    small_heap.push(2);
    small_heap.push(3);
    small_heap.push(5);
    small_heap.push(0);
    while(!small_heap.empty()){
        cout<<small_heap.top()<<endl;
        small_heap.pop();
        
    }

}

输出

0
2
3
5

priority_queue 操作:
q.size();//返回q里元素个数
q.empty();//返回q是否为空，空则返回1，否则返回0
q.push(k);//在q的末尾插入k
q.pop();//删掉q的第一个元素
q.top();//返回q的第一个元素

参考：http://www.cplusplus.com/reference/functional/less/