title: Count Index Pairs Equal Elements Array 1
signature: function count_index_pairs_equal_elements_array_1(arr, n)
test_code: 
  
  -- SOLUTION CODE
  -- ============================================
  PLACEHOLDER_CODE_BODY
  
  -- TESTING CODE 
  -- ============================================
  function isCorrect(actual, expected)
      if type(expected) ~= type(actual) then
          return false
      end
      
      if type(expected) == 'table' then
          for k,v_expected in pairs(expected) do
              
              if actual[k] == nil then
                  return false
              end
              local v_actual = actual[k]
              if not isCorrect(v_actual, v_expected) then
                  return false
              end
              actual[k]=nil
          end
      
          if next(actual) then 
              return false
          end
          return true
      else
          return actual == expected
      end
  end
  
  function validateSolution(actual, expected)
      return isCorrect(actual,expected)
  end
  
  function driver(arr, n, expected)
      local exec_result;
      local status, error_msg = pcall(function () 
          exec_result=PLACEHOLDER_FN_NAME(arr, n) 
      end)
      if status then
          if validateSolution(exec_result,expected) then
              return "PASSED"
          end
          return "FAILED"
      else
          return string.format("ERROR=%s",string.gsub(error_msg,".*:[%d]+: ",""))
      end
  end
      
  function main()
      result = driver({5, 11, 18, 22, 40, 46, 50, 51, 53, 55, 64, 67, 73, 78, 86}, 14, 0)
      print(string.format("TEST-0...%s",result))
  
      result = driver({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)
      print(string.format("TEST-1...%s",result))
  
      result = driver({0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1}, 13, 56)
      print(string.format("TEST-2...%s",result))
  
      result = driver({93, 23, 62, 64, 31, 78, 99}, 4, 0)
      print(string.format("TEST-3...%s",result))
  
      result = driver({-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)
      print(string.format("TEST-4...%s",result))
  
      result = driver({0}, 0, 0)
      print(string.format("TEST-5...%s",result))
  
      result = driver({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)
      print(string.format("TEST-6...%s",result))
  
      result = driver({-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)
      print(string.format("TEST-7...%s",result))
  
      result = driver({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)
      print(string.format("TEST-8...%s",result))
  
      result = driver({31, 5}, 1, 0)
      print(string.format("TEST-9...%s",result))
  
  end
  
  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;
  }