结论

类型 自带排序 定义cmp结构（为<） greater<int> 定义bool cmp函数（为<）
set 升序 升序 降序 \
priority_queue 降序 降序 升序 \
sort 升序 \ \ 升序

表中 \ 表示这种语法无法适用于该排序。

测试代码

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//test for set
#include<bits/stdc++.h>
using namespace std;


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

int main()
{
    set<int> test1;、
    set<int,cmp> test3;
    set<int, greater<int> > test4;
    test1.insert(1);
    test3.insert(1);
    test4.insert(1);
    test1.insert(2);
    test3.insert(2);
    test4.insert(2);

    cout << *test1.begin() << " " << *test3.begin() << " " << *test4.begin();
//output:1 1 2
}
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//test for priority_queue
#include<bits/stdc++.h>
using namespace std;

struct str{int v;};
bool operator < (str a, str b) { return a.v < b.v; };
struct cmp {bool operator()(int a, int b){return a < b;}};


int main()
{
    priority_queue<int> test1;
    priority_queue<int, vector<int>, cmp> test2;
    priority_queue<int, vector<int>, greater<int> > test3;
    test1.push(1);
    test2.push(1);
    test3.push(1);
    test1.push(2);
    test2.push(2);
    test3.push(2);
    cout << test1.top() << " " << test2.top() << " " << test3.top();
}
//output: 2 2 1
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//test for std::sort
#include<bits/stdc++.h>
using namespace std;

bool cmp(int a, int b) { return a < b; };

int main()
{
    int a[2] = { 0,1 };
    sort(a, a + 1);
    cout << a;
    sort(a, a+1, cmp);
    cout << a;
}
//output: 0 0