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367. Valid Perfect Square

Difficulty Topics

Description

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

valid-perfect-square.py
class Solution:
    def isPerfectSquare(self, num: int) -> bool:
        left, right = 1, 10 ** 18

        while left < right:
            mid = left + (right - left) // 2

            if mid * mid >= num:
                right = mid
            else:
                left = mid + 1

        return left * left == num