C++ priority_queue用法

std::priority_queue

template <class T, class Container = vector<T>,
  class Compare = less<typename Container::value_type> > class priority_queue;

 

C++ STL默认的priority_queue是将优先级最大的放在队列最前面，也即是最大堆.

【代码示例】

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <map>
#include <unordered_map>
#include <string>
#include <queue>
using namespace std;


/**
默认比较函数为less, 大顶堆
**/
void defaultCmpLess() {
    cout << "=========defaultCmpLess(big heap)========" << endl;
    priority_queue<int> q;
    for (int i = 0; i < 10; i++) {
        q.push(rand()%20);
    }

    while (!q.empty()) {
        cout << q.top() << " ";
        q.pop();
    }
    cout <<endl;

}

/**
使用greater比较函数，小顶堆
**/
void useCmpGreater() {
    cout << "=========useCmpGreater(small heap)========" << endl;
    priority_queue<int, vector<int>, greater<int> > q;
    for (int i = 0; i < 10; i++) {
        q.push(rand()%20);
    }

    while (!q.empty()) {
        cout << q.top() << " ";
        q.pop();
    }
    cout <<endl;
}
//=========================
/**
自构建比较函数
**/
struct cmp2
{
    bool operator()(int a, int b) {
        return a < b;
    }
};

void designCmp() {
    cout << "=========designCmp========" << endl;
    cout << "operator a<b" << endl;
    priority_queue<int, vector<int>, cmp2 > q;

    for (int i = 0; i < 10; i++) {
        q.push(rand()%20);
    }

    while (!q.empty()) {
        cout << q.top() << " ";
        q.pop();
    }
    cout <<endl;
}





int main(int argc, char const *argv[])
{   
    defaultCmpLess();
    useCmpGreater();
    designCmp();
}


/**
=========defaultCmpLess(big heap)========
18 18 13 12 10 9 9 7 4 3
=========useCmpGreater(small heap)========
0 0 2 3 5 7 7 9 12 12
=========designCmp========
operator a<b
17 16 14 13 12 11 8 7 5 5