一个FLAG #16# 优先队列

例子

#include <iostream>
#include <queue>
#include <vector>
using namespace std;

struct cmp {
    bool operator() (const int a, const int b) const {
        return a % 10 < b % 10;  
    }
};

int main()
{
    // 默认的优先队列。数值越大优先级越高 
    priority_queue<int> pq;
    pq.push(2);
    pq.push(123);
    pq.push(1235);
    pq.push(55);
    pq.push(1230);
    cout << pq.top() << endl; pq.pop(); // => 1235
    cout << pq.top() << endl; pq.pop(); // => 1230
    cout << pq.top() << endl; pq.pop(); // => 123
    cout << pq.top() << endl; pq.pop(); // => 55
    cout << pq.top() << endl; pq.pop(); // => 2
    
    cout << pq.top() << endl; pq.pop(); // => 2
    cout << pq.top() << endl; pq.pop(); // => 2
    cout << pq.top() << endl; pq.pop(); // => 2
    
    cout << " ==================================== == =" << endl;
    // 越小的整数优先级越高
    priority_queue<int, vector<int>, greater<int> > pq2; 
    pq2.push(2);
    pq2.push(123);
    pq2.push(55);
    cout << pq2.top() << endl; pq2.pop(); // => 2
    cout << pq2.top() << endl; pq2.pop(); // => 55
    cout << pq2.top() << endl; pq2.pop(); // => 123
    
    cout << " ==================================== == =" << endl;
    // 自定义的优先队列，个位越大的优先级越高 
    priority_queue<int, vector<int>, cmp> pq3;
    pq3.push(2);
    pq3.push(123);
    pq3.push(55);
    cout << pq3.top() << endl; pq3.pop(); // => 55
    cout << pq3.top() << endl; pq3.pop(); // => 123
    cout << pq3.top() << endl; pq3.pop(); // => 2
        
    return 0;
}