#include<bits/stdc++.h>
using namespace std;
set<int> s1={1, 2, 3},s2={2,3,1,1},s3={1,2,100},s4={3,4,5};
map<set<int>,int>mp1,mp2;
int main(){
	mp1[s3]=9,mp1[s1]=1,mp2[s2]=1,mp2[s4]=5;
	cout<<(mp1<mp2)<<' ';
	cout<<mp2[s3]<<' ';
	cout<<(mp1<=mp2)<<endl; 
	return 0;
} 

输出结果是

1 0 0

不太理解原因，还望大佬们赐教