title: Find Repetitive Element 1 N 1 2
signature: function find_repetitive_element_1_n_1_2(arr, n)
test_code: using Printf
  
  # SOLUTION CODE
  # ============================================
  PLACEHOLDER_CODE_BODY
  
  # TESTING CODE 
  # ============================================
  function validate_solution(actual, expected)
      return actual == expected
  end
  
  function driver(arr, n, expected)
      try
  
          if validate_solution(PLACEHOLDER_FN_NAME(arr, n), expected)
              return "PASSED";
          end
          return "FAILED";
      catch exception_obj
          return string(Base.typename(typeof(exception_obj)).wrapper);
      end
  end
  
  function main()
      
      result = driver([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-0...%s\n",result);
      
      result = driver([46, 2, 62, 60, 92, 4, 26, 66, 66, 90, 26, -14, 76, -20, -68], 8, 46);
      @printf("TEST-1...%s\n",result);
      
      result = driver([0, 0, 0, 1, 1, 1, 1, 1], 4, 1);
      @printf("TEST-2...%s\n",result);
      
      result = driver([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-3...%s\n",result);
      
      result = driver([-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-4...%s\n",result);
      
      result = driver([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-5...%s\n",result);
      
      result = driver([1, 14, 15, 15, 21, 34, 38, 39, 41, 50, 60, 74, 96, 97], 7, 25);
      @printf("TEST-6...%s\n",result);
      
      result = driver([96, -12, -16, -52], 3, 103);
      @printf("TEST-7...%s\n",result);
      
      result = driver([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-8...%s\n",result);
      
      result = driver([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);
      @printf("TEST-9...%s\n",result);
      
  end
  
  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;
  }