优先队列的基本用法(java和c++）

#include <bits/stdc++.h>
#define ll long long
#define mod 1000000007
using namespace std;
//熟悉一下优先队列的基本用法
int main()
{
    int n;cin>>n;
    priority_queue<int>q;
    int j;
    for(int i=1;i<=n;i++)
    {
        cin>>j;
        q.push(j);
    }
    while(!q.empty())
    {
        cout<<q.top()<<endl;
        q.pop();
    }
    return 0;
}

　　java：

import java.math.BigInteger;
import java.util.*;

public class CF470C {

    public static void main(String[] args) {
        PriorityQueue<String> queue = new PriorityQueue<String>();
        queue.add("C");
        queue.add("C++");
        queue.add("Python");
        queue.add("Java");
        // Printing the most priority element
        System.out.println("Head value using peek function:"
                                              +queue.peek());
        // Printing all elements
        System.out.println("The queue elements");
        Iterator itr=queue.iterator();
        while(itr.hasNext())
            System.out.println(itr.next());
        // Removing the top priority element (or head) and
        // printing the modified pQueue
        queue.poll();
        System.out.println("After removing an element" +
                "with poll function:");
        Iterator<String> itr2 = queue.iterator();
        while (itr2.hasNext())
            System.out.println(itr2.next());
        // // Removing Java
        queue.remove("C");
        System.out.println("after removing Java with" +
                " remove function:");
        Iterator<String> itr3 = queue.iterator();
        while (itr3.hasNext())
            System.out.println(itr3.next());
        // // Check if an element is present
        boolean b=queue.contains("C");
        System.out.println ( "Priority queue contains C" +
                "ot not?: " + b);
        // get objects from the queue in an array and
        // print the array
        Object[]arr=queue.toArray();
        System.out.println("Value in array: ");
        for(int i=0;i<arr.length;i++)
            System.out.println("Value: "+arr[i].toString());


    }
}

　　注意：Java中的优先队列没有排序功能，若要排序，请用：

As you can see in the PriorityQueue javadoc: The Iterator provided in method iterator() is not guaranteed to traverse the elements of the priority queue in any particular order. If you need ordered traversal, consider using Arrays.sort(pq.toArray()). That's because java.util.PriorityQueue implements a binary heap.

应用：

Applications :
Implementing Dijkstra’s and Prim’s algorithms.

https://www.geeksforgeeks.org/priority-queue-class-in-java-2/

例题：

//��CF 947B
#include<iostream>
#include<cstdio>
#include<fstream>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<cmath>
#include<cstring>
#include<cstdlib>
using namespace std;
typedef long long LL;
typedef double DB;
const int N = 111111;
int n,a[N],b[N];
priority_queue<LL,vector<LL>,greater<LL> > Q;
int main()
{
	int i,x;
	LL w,ans;
	scanf("%d",&n);
	for(i=1;i<=n;i=i+1)
		scanf("%d",a+i);
	for(i=1;i<=n;i=i+1)
		scanf("%d",b+i);
	w=0,x=0;
	for(i=1;i<=n;i=i+1){
		ans=0;
		Q.push(w+a[i]);
		x++;
		while(!Q.empty()&&Q.top()<=w+b[i]){
			ans+=Q.top()-w;
			Q.pop();
			x--;
		}
		w+=b[i];
		ans+=(LL)b[i]*x;
		cout<<ans<<' ';
	}
	return 0;
}