input: Write a python function to check if a number is a perfect square.
  assert isPerfectSquare(25) == True
  assert isPerfectSquare(16) == True
  assert isPerfectSquare(14) == False
  assert isPerfectSquare(0) == True
  assert isPerfectSquare(1) == True
output: def isPerfectSquare(num):
      if num < 0:
          return False
      root = int(num ** 0.5)
      return root * root == num