Cpp实现：

#include <cstdio>
#include <queue>

using namespace std;

struct Node
{
    int a, b;

    Node() {}

    Node(int a, int b) : a(a), b(b) {}

    bool operator>(const Node& t) const
    {
        if (a > t.a) return true;
        else if (a < t.a) return false;
        else b > t.b;
    }

    bool operator<(const Node& t) const
    {
        if (a < t.a) return true;
        else if (a > t.a) return false;
        else return b < t.b;
    }
};

priority_queue<Node, vector<Node>, greater<Node>> pq;
//priority_queue<Node> pq;

int main()
{
    pq.push(Node(2, 3));
    pq.push(Node(2, 2));
    pq.push(Node(1, 1));
//    pq.push(Node(1, 1));
//    pq.push(Node(2, 2));
//    pq.push(Node(2, 3));
    while (!pq.empty())
    {
        printf("%d %d\n", pq.top().a, pq.top().b);
        pq.pop();
    }
    return 0;
}

Java实现：

import java.util.*;

public class Main {
    // jdk1.8 用lambda: 默认升序排列：o1 < o2 => o1 - o2 < 0，降序排列：o2 - o1
    static PriorityQueue<Integer> pq = new PriorityQueue<>((o1, o2) -> o1 - o2);
    // jdk1.6 用匿名类: 默认升序排列：o1 - o2，降序排列：o2 - o1
    static PriorityQueue<Integer> pq1 = new PriorityQueue<>(new Comparator<Integer>() {
        @Override
        public int compare(Integer o1, Integer o2) {
            return o1 - o2;
        }
    });
}

import java.io.*;
import java.util.Comparator;
import java.util.PriorityQueue;

public class Main
{
    static class Node implements Comparator<Node>
    {
        int a, b;

        public Node() {}

        public Node(int a, int b)
        {
            this.a = a;
            this.b = b;
        }

        @Override
        public int compare(Node o1, Node o2)
        {
            if (o1.a < o2.a) return -1;
            else if (o1.a > o2.a) return 1;
            else return o1.b - o2.b;
        }

//        @Override
//        public int compare(Node o1, Node o2)
//        {
//            if (o1.a > o2.a) return -1;
//            else if (o1.a < o2.a) return 1;
//            else return o2.b - o1.b;
//        }
    }

    static PriorityQueue<Node> pq = new PriorityQueue<>(new Node());
    static PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));

    public static void main(String[] args) throws IOException
    {
        pq.add(new Node(2, 3));
        pq.add(new Node(2, 2));
        pq.add(new Node(1, 1));
//        pq.add(new Node(1, 1));
//        pq.add(new Node(2, 2));
//        pq.add(new Node(2, 3));
        while (!pq.isEmpty())
        {
            pw.printf("%d %d\n", pq.peek().a, pq.peek().b);
            pq.poll();
        }
        pw.close();
    }
}