title: Find Repetitive Element 1 N 1 2
signature: function findRepetitiveElement1N12($arr, $n) {
test_code: <?php
  
  
  // SOLUTION CODE 
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  function validateSolution($actual, $expected){
      return serialize($actual) == serialize($expected);
  }
  
  function driver($arr, $n, $expected){
      try{
        if (validateSolution(PLACEHOLDER_FN_NAME($arr, $n), $expected)){
          return "PASSED";
        }
        return "FAILED";
      }
      catch (Exception $exception_obj) {
        return get_class($exception_obj);
      }
  }
  
  function main(){
      printf("TEST-0...%s\n",driver(
        array(2, 2, 4, 5, 5, 7, 7, 7, 8, 11, 14, 15, 18, 19, 20, 25, 25, 29, 29, 31, 32, 32, 33, 38, 42, 48, 52, 55, 60, 61, 63, 71, 74, 78, 82, 82, 84, 84, 87, 87, 88, 90, 93, 94, 94), 31, 
        52));
      
      printf("TEST-1...%s\n",driver(
        array(46, 2, 62, 60, 92, 4, 26, 66, 66, 90, 26, -14, 76, -20, -68), 8, 
        46));
      
      printf("TEST-2...%s\n",driver(
        array(0, 0, 0, 1, 1, 1, 1, 1), 4, 
        1));
      
      printf("TEST-3...%s\n",driver(
        array(87, 67, 11, 47, 64, 81, 94, 75, 58, 77, 18, 2, 85, 26, 6, 44, 55, 19, 46, 49, 5, 69, 44, 12, 42, 66, 46, 9, 26, 49, 68, 95, 6, 9, 11, 72, 5, 67), 34, 
        28));
      
      printf("TEST-4...%s\n",driver(
        array(-98, -94, -92, -82, -78, -64, -62, -58, -52, -44, -40, -38, -8, 6, 10, 20, 22, 28, 30, 30, 36, 54, 54, 58, 64, 68, 76, 78, 84, 88, 90, 94, 96), 29, 
        -32));
      
      printf("TEST-5...%s\n",driver(
        array(1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 1), 17, 
        16));
      
      printf("TEST-6...%s\n",driver(
        array(1, 14, 15, 15, 21, 34, 38, 39, 41, 50, 60, 74, 96, 97), 7, 
        25));
      
      printf("TEST-7...%s\n",driver(
        array(96, -12, -16, -52), 3, 
        103));
      
      printf("TEST-8...%s\n",driver(
        array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1), 21, 
        21));
      
      printf("TEST-9...%s\n",driver(
        array(66, 21, 21, 59, 78, 8, 46, 41, 16, 32, 97, 93, 32, 86, 91, 61, 67, 61, 97, 49, 66, 35, 24, 35, 65, 45, 83), 25, 
        9));
      
  }
  
  main();
  ?>
source_py: def find_repetitive_element_1_n_1_2(arr, n):
      res = 0
      for i in range(0, (n - 1)):
          res = ((res ^ (i + 1)) ^ arr[i])
      res = (res ^ arr[(n - 1)])
      return res
source_cpp: int find_repetitive_element_1_n_1_2(vector<int> arr, int n) {
    int res = 0;
    for ( int i = 0;
    i < n - 1;
    i ++ ) res = res ^ ( i + 1 ) ^ arr [ i ];
    res = res ^ arr [ n - 1 ];
    return res;
  }