only_nonrepeating_arr

arr = [1, 2, 1, 2, 3]
 
ele = arr[0]
for i in range(1, len(arr)):
    ele ^= arr[i]
 
print(ele)

#include <iostream>
 
using namespace std;
 
int main() {
  int arr[] = {1, 2, 3, 1, 2};
  int n = sizeof(arr) / sizeof(arr[0]);
 
  int ele = arr[0];
 
  for (int i = 1; i < n; i++) {
    ele ^= arr[i];
  }
 
  cout << ele;
}