title: Find Repetitive Element 1 N 1 2
signature: class Solution {
  
      public int FindRepetitiveElement1N12(List<int> arr, int n) {
test_code: using System;
  using System.Numerics;
  using System.Diagnostics;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using System.Security.Cryptography;
  using System.Web.UI;
  using System.Web.Script.Serialization;
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  namespace EvaluatePrediction {
      class TestRunner {
          public bool ValidateSolution(int actual, int expected){
              return new JavaScriptSerializer().Serialize(actual) == new JavaScriptSerializer().Serialize(expected);
          }
  
          public string driver(List<int> arr, int n, int expected){
              try{
                PLACEHOLDER_CLS_NAME solution_cls = new PLACEHOLDER_CLS_NAME();
                int pred_result = solution_cls.PLACEHOLDER_FN_NAME(arr, n); 
                if (ValidateSolution(
                      pred_result,
                      expected)){
                  return "PASSED";
                }
                return "FAILED";
              } 
              catch (Exception exception_obj)
              {
                return exception_obj.GetType().FullName;
              }
          }
          static void Main(string[] args) {
              TestRunner runner = new TestRunner();
              String result;
              result = runner.driver(
                  new List<int>{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
              );
              Console.WriteLine(string.Format(
                  "TEST-0...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{46, 2, 62, 60, 92, 4, 26, 66, 66, 90, 26, -14, 76, -20, -68}, 8, 
                  46
              );
              Console.WriteLine(string.Format(
                  "TEST-1...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{0, 0, 0, 1, 1, 1, 1, 1}, 4, 
                  1
              );
              Console.WriteLine(string.Format(
                  "TEST-2...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{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
              );
              Console.WriteLine(string.Format(
                  "TEST-3...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{-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
              );
              Console.WriteLine(string.Format(
                  "TEST-4...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{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
              );
              Console.WriteLine(string.Format(
                  "TEST-5...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{1, 14, 15, 15, 21, 34, 38, 39, 41, 50, 60, 74, 96, 97}, 7, 
                  25
              );
              Console.WriteLine(string.Format(
                  "TEST-6...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{96, -12, -16, -52}, 3, 
                  103
              );
              Console.WriteLine(string.Format(
                  "TEST-7...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{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
              );
              Console.WriteLine(string.Format(
                  "TEST-8...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{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
              );
              Console.WriteLine(string.Format(
                  "TEST-9...{0}",
                  result)
              );
          }
      }
  }
  
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;
  }