小编Nee*_*lex的帖子

选择排序的意义是什么？即使在最好的情况下，它的时间复杂度也是 O(n^2)。那么为什么它仍然盛行？

#include <iostream>
using namespace std;

int main(){
    int t;
    long long int n,res,x;
    scanf("%d",&t);
    while(t--){
            scanf("%lld",&n);
            res=0;


    for(int i=0;i<n;i++){
            scanf("%lld",&x);
            res^=x;
    }
    if(res==0)
        printf("-1\n");
    else 
        printf("%lld\n",res);

}
return 0;
}

this same program when i used cin and cout was timed out in hackerearth. But passed with scanf and printf.