title: Find Repetitive Element 1 N 1 2
signature: fun findRepetitiveElement1N12(arr: ArrayList<Int>, n: Int): Int {
test_code: package main
  
  import kotlin.text.*
  import kotlin.math.*
  
  
  // SOLUTION CODE
  // ===================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE
  // ===================================
  fun validateSolution(actual:Int, expected:Int):Boolean{
    return actual.equals(expected)
  }
  fun driver(arr: ArrayList<Int>, n: Int, expected:Int):String {
      try{
        if (validateSolution(PLACEHOLDER_FN_NAME(arr, n), expected)) {
                return "PASSED"
        }
        return "FAILED"
      } catch (e: Exception){
        return e::class.simpleName as String
      }
  
  }
  
  fun main() {
      var result: String = ""
      result = driver(arrayListOf(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)
      println("TEST-0...${result}")
      
      result = driver(arrayListOf(46, 2, 62, 60, 92, 4, 26, 66, 66, 90, 26, -14, 76, -20, -68), 8, 46)
      println("TEST-1...${result}")
      
      result = driver(arrayListOf(0, 0, 0, 1, 1, 1, 1, 1), 4, 1)
      println("TEST-2...${result}")
      
      result = driver(arrayListOf(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)
      println("TEST-3...${result}")
      
      result = driver(arrayListOf(-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)
      println("TEST-4...${result}")
      
      result = driver(arrayListOf(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)
      println("TEST-5...${result}")
      
      result = driver(arrayListOf(1, 14, 15, 15, 21, 34, 38, 39, 41, 50, 60, 74, 96, 97), 7, 25)
      println("TEST-6...${result}")
      
      result = driver(arrayListOf(96, -12, -16, -52), 3, 103)
      println("TEST-7...${result}")
      
      result = driver(arrayListOf(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)
      println("TEST-8...${result}")
      
      result = driver(arrayListOf(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)
      println("TEST-9...${result}")
      
          
  }
  
  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;
  }