View Code of Problem 3929

#include<iostream>
#include<math.h>
#include<string.h>
using namespace std;
int main(){
  	int T;
  	cin>>T;
  	while(T--){
  		int a[10010];
  		long long b[10010];
  		memset(a,0,sizeof(a));
  		memset(b,0,sizeof(b));
  		int n;
  		cin>>n;
  		long long num;
  		int sum;
  		for(int i=0;i<n;i++){
  			cin>>a[i];
  			b[a[i]]++;
		  }
		for(int i=0;i<n;i++){
			if(b[a[i]]%2==1){
				//cout<<a[i]<<endl;
				sum^=a[i];
			}
		}
		cout<<sum<<endl;
	  }
}