title: Count Index Pairs Equal Elements Array 1
signature: function countIndexPairsEqualElementsArray1($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(5, 11, 18, 22, 40, 46, 50, 51, 53, 55, 64, 67, 73, 78, 86), 14, 
        0));
      
      printf("TEST-1...%s\n",driver(
        array(14, -98, 98, 58, -82, 90, -80, -56, -30, -36, -56, -30, -58, 68, 72, -76, 38, -90, -72, 4, -32, 32, -28, 2, 12, -72, 54, 2, 0, -74, 8, 12, 46, 72, -84, -66, 70, 18, 26, 72, -26, 44, -8, 20, -32, -56, 28), 24, 
        2));
      
      printf("TEST-2...%s\n",driver(
        array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1), 13, 
        56));
      
      printf("TEST-3...%s\n",driver(
        array(93, 23, 62, 64, 31, 78, 99), 4, 
        0));
      
      printf("TEST-4...%s\n",driver(
        array(-94, -94, -92, -86, -84, -76, -76, -68, -66, -56, -56, -54, -50, -46, -38, -34, -34, -30, -26, -18, -16, 2, 8, 42, 52, 54, 56, 64, 68, 82, 82, 82, 94, 96, 98), 19, 
        4));
      
      printf("TEST-5...%s\n",driver(
        array(0), 0, 
        0));
      
      printf("TEST-6...%s\n",driver(
        array(3, 18, 18, 20, 21, 23, 24, 27, 35, 36, 38, 40, 46, 50, 50, 51, 52, 53, 59, 61, 63, 63, 65, 66, 68, 68, 70, 71, 74, 75, 96, 98), 19, 
        2));
      
      printf("TEST-7...%s\n",driver(
        array(-68, 40, 16, 50, 36, 42, -20, -46, -92, 4, -18, -12, 48, 0, -46, 64, -74, -50, 42, 44, -56, 28, -10, 78, 62, 70, -60, 12, -44, -78), 23, 
        2));
      
      printf("TEST-8...%s\n",driver(
        array(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, 1, 1, 1, 1, 1, 1, 1), 30, 
        211));
      
      printf("TEST-9...%s\n",driver(
        array(31, 5), 1, 
        0));
      
  }
  
  main();
  ?>
source_py: def count_index_pairs_equal_elements_array_1(arr, n):
      mp = dict()
      for i in range(n):
          if (arr[i] in mp.keys()):
              mp[arr[i]] += 1
          else:
              mp[arr[i]] = 1
      ans = 0
      for it in mp:
          count = mp[it]
          ans += ((count * (count - 1)) // 2)
      return ans
source_cpp: int count_index_pairs_equal_elements_array_1(vector<int> arr, int n) {
    unordered_map < int, int > mp;
    for ( int i = 0;
    i < n;
    i ++ ) mp [ arr [ i ] ] ++;
    int ans = 0;
    for ( auto it = mp . begin ( );
    it != mp . end ( );
    it ++ ) {
      int count = it -> second;
      ans += ( count * ( count - 1 ) ) / 2;
    }
    return ans;
  }