Given a positive integer num, write a function which returns True if num is a perfect square else False.
Follow up: Do not use any built-in library function such as sqrt.
Example 1:
Input: num = 16
Output: true
Example 2:
Input: num = 14
Output: false
Constraints:
- 1 <= num <= 2^31 – 1
Solution in python:
class Solution:
def isPerfectSquare(self, num: int) -> bool:
def helper(left, right):
mid = (left + right) // 2
if left <= right:
if mid**2 < num:
return helper(mid+1, right)
elif mid**2 > num:
return helper(left, mid-1)
else:
return True
else: return False
return helper(1, num)
留言