#include <thread>

using namespace std;

string s = "1234567890";

set<string> Set;

Set.insert(s.substr(0, 3));

Set.insert(s.substr(3, 3));

Set.insert(s.substr(6, 3));

cout << *Set.begin() << endl;

cout << *Set.rbegin() << endl;

void demo_multiset() {

}

https://www.cnblogs.com/grandyang/p/14167726.html

class Robot {

};

void dfs(Robot& robot, set<pair<int, int>>& visited, int i, int j, int dir) {

}

int main(void) {