19 .find non – duplicate number

 

Observation : a^a == 0

Code :

#include<bits/stdc++.h> using namespace std; //all number will be duplicate accept one int main() {     int t,n,i,x=0;     cin>>t;     while (t--)     {         int n,arr[100];         cin >> n; //n - odd number         for(int i=0;i<n;i++) cin >> arr[i];           int xo = 0;         for(int i=0;i<n;i++) /// O(n*n)         {            xo=xo^arr[i];         }               cout << xo << "\n";     } }