对于基本数据类型

priority_queue<int> q;  //默认从大到小（大根堆）
priority_queue<int, vector<int>, less<int>> q;  //从大到小排序（大根堆）
priority_queue<int, vector<int>, greater<int>> q;   //从小到大排序（小根堆）

自定义优先级（$struct$）

1. 值小的优先级高（小根堆）

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int N = 1e5 + 10;

struct Node
{
    int x, y;
}nodes[N];

struct cmp1
{
    bool operator () (const Node &u, const Node &v)
    {
        return u.x > v.x;
    }
};

int main()
{
    nodes[0] = {-3, -9};
    nodes[1] = {1, 2};
    nodes[2] = {9, 4};
    nodes[3] = {8, 12};
    nodes[4] = {-19, 23};
    priority_queue<Node, vector<Node>, cmp1> q;

    for (int i = 0; i <= 4; i ++)
        q.push(nodes[i]);

    while (q.size())
    {
        auto t = q.top();
        q.pop();
        printf("x: %d ---- y: %d\n", t.x, t.y);
    }

    system("pause");
    return 0;
}

• 输出结果
  

• 值大的优先级高（大根堆）

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int N = 1e5 + 10;

struct Node
{
    int x, y;
}nodes[N];

struct cmp2
{
    bool operator () (const Node &u, const Node &v)
    {
        return u.x < v.x;
    }
};

int main()
{
    nodes[0] = {-3, -9};
    nodes[1] = {1, 2};
    nodes[2] = {9, 4};
    nodes[3] = {8, 12};
    nodes[4] = {-19, 23};
    priority_queue<Node, vector<Node>, cmp2> q;

    for (int i = 0; i <= 4; i ++)
        q.push(nodes[i]);

    while (q.size())
    {
        auto t = q.top();
        q.pop();
        printf("x: %d ---- y: %d\n", t.x, t.y);
    }

    system("pause");
    return 0;
}

• 输出结果
  

重载 $<$ 运算符

1. 值小的优先级高（小根堆）

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int N = 1e5 + 10;

struct Node
{
    int x, y;
    bool operator < (const Node &u) const
    {
        return x > u.x;
    }
}nodes[N];


int main()
{
    nodes[0] = {-3, -9};
    nodes[1] = {1, 2};
    nodes[2] = {9, 4};
    nodes[3] = {8, 12};
    nodes[4] = {-19, 23};
    priority_queue<Node> q;

    for (int i = 0; i <= 4; i ++)
        q.push(nodes[i]);

    while (q.size())
    {
        auto t = q.top();
        q.pop();
        printf("x: %d ---- y: %d\n", t.x, t.y);
    }

    system("pause");
    return 0;
}

• 输出结果
  

• 值大的优先级高（大根堆）

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int N = 1e5 + 10;

struct Node
{
    int x, y;
    bool operator < (const Node &u) const
    {
        return x < u.x;
    }
}nodes[N];


int main()
{
    nodes[0] = {-3, -9};
    nodes[1] = {1, 2};
    nodes[2] = {9, 4};
    nodes[3] = {8, 12};
    nodes[4] = {-19, 23};
    priority_queue<Node> q;

    for (int i = 0; i <= 4; i ++)
        q.push(nodes[i]);

    while (q.size())
    {
        auto t = q.top();
        q.pop();
        printf("x: %d ---- y: %d\n", t.x, t.y);
    }

    system("pause");
    return 0;
}

• 输出结果
  

自定义排序

1. 根据元素和进行降序排序

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;
typedef pair<int, int> PII;
const int N = 1010;

struct Gift
{
    int p, s;
    bool operator < (const Gift& u) const
    {
        return p + s > u.p + u.s;
    }
}gift[N];

int main()
{
    gift[0] = {0, 2};
    gift[1] = {2, 3};
    gift[2] = {0, 1};

    sort(gift, gift + 3);
    for (int i = 0; i < 3; i ++)
    {
        printf("%d %d\n", gift[i].p, gift[i].s);
    }
    return 0;
}

1. 根据元素和进行升序排序

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;
typedef pair<int, int> PII;
const int N = 1010;

struct Gift
{
    int p, s;
    bool operator < (const Gift& u) const
    {
        return p + s < u.p + u.s;
    }
}gift[N];

int main()
{
    gift[0] = {0, 2};
    gift[1] = {2, 3};
    gift[2] = {0, 1};

    sort(gift, gift + 3);
    for (int i = 0; i < 3; i ++)
    {
        printf("%d %d\n", gift[i].p, gift[i].s);
    }
    return 0;
}