还是可以用set

#include<bits/stdc++.h>
using namespace std;
int n,k,ans;
set<int>a;
set<int>::iterator it;
bool b;

int main(){
	freopen("knumber.in","r",stdin);
	freopen("knumber.out","w",stdout);
	scanf("%d%d",&n,&k);
	for(int i=1;i<=n;i++){
		int x;
		scanf("%d",&x);
		a.insert(x);
	}
	for(it=a.begin();it!=a.end();it++){
		ans++;
		if(ans==k){
			printf("%d",*it);
			b=1;
			break;
		}
	}
	if(!b) printf("NO RESULT");
	return 0;
}