title: Count Pairs Difference Equal K
signature: function count_pairs_difference_equal_k(arr, n, k)
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, k, expected)
      local exec_result;
      local status, error_msg = pcall(function () 
          exec_result=PLACEHOLDER_FN_NAME(arr, n, k) 
      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({9, 14, 17, 19, 22, 23, 23, 27, 30, 31, 34, 37, 37, 39, 39, 42, 57, 61, 68, 73, 77, 79, 91, 96, 97}, 19, 19, 3)
      print(string.format("TEST-0...%s",result))
  
      result = driver({-78, -42, 28, -88, 18, -52}, 3, 4, 0)
      print(string.format("TEST-1...%s",result))
  
      result = driver({0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1}, 16, 14, 0)
      print(string.format("TEST-2...%s",result))
  
      result = driver({8, 46, 57, 28, 80, 2, 75, 57, 83, 45, 32, 49, 77, 30, 94, 33, 23, 29, 35, 81, 85}, 15, 11, 3)
      print(string.format("TEST-3...%s",result))
  
      result = driver({-90, -72, -72, -62, -62, -54, -54, -52, -48, -38, -22, -22, -22, -12, -12, -8, -8, -8, -6, -6, -2, 6, 12, 26, 26, 28, 28, 38, 40, 48, 52, 52, 58, 60, 68, 70, 72, 76, 76, 76, 92}, 22, 25, 0)
      print(string.format("TEST-4...%s",result))
  
      result = driver({0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1}, 45, 39, 0)
      print(string.format("TEST-5...%s",result))
  
      result = driver({3, 13, 19, 23, 27, 32, 49, 52, 54, 57, 58, 58, 63, 67, 68, 68, 69, 70, 75, 80, 86, 90, 91, 95}, 19, 21, 2)
      print(string.format("TEST-6...%s",result))
  
      result = driver({-56, 40, -66, 42, 8, -40, -8, -42}, 7, 6, 0)
      print(string.format("TEST-7...%s",result))
  
      result = driver({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}, 16, 28, 0)
      print(string.format("TEST-8...%s",result))
  
      result = driver({99, 12, 90, 10, 86, 86, 81, 19, 1, 1, 98, 82, 34, 39, 34, 1, 54, 47, 39, 82, 21, 50, 82, 41, 98, 47, 88, 46, 72, 28, 28, 29, 60, 87, 92, 53, 93, 29, 74, 75, 11, 32, 48, 47, 85, 16, 20}, 24, 45, 3)
      print(string.format("TEST-9...%s",result))
  
  end
  
  main()
source_py: def count_pairs_difference_equal_k(arr, n, k):
      count = 0
      for i in range(0, n):
          for j in range((i + 1), n):
              if (((arr[i] - arr[j]) == k) or ((arr[j] - arr[i]) == k)):
                  count += 1
      return count
source_cpp: int count_pairs_difference_equal_k(vector<int> arr, int n, int k) {
    int count = 0;
    for ( int i = 0;
    i < n;
    i ++ ) {
      for ( int j = i + 1;
      j < n;
      j ++ ) if ( arr [ i ] - arr [ j ] == k || arr [ j ] - arr [ i ] == k ) count ++;
    }
    return count;
  }