README_EN.md

367. Valid Perfect Square

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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

Solutions

Python3

class Solution:
    def isPerfectSquare(self, num: int) -> bool:
        left, right = 1, num
        while left < right:
            mid = left + ((right - left) >> 1)
            if num // mid <= mid:
                right = mid
            else:
                left = mid + 1
        return left * left == num

Java

class Solution {
    public boolean isPerfectSquare(int num) {
        int left = 1, right = num;
        while (left < right) {
            int mid = (left + right) >>> 1;
            if (num / mid <= mid) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return left * left == num;
    }
}

C++

class Solution {
public:
    bool isPerfectSquare(int num) {
        long left = 1, right = num;
        while (left < right) {
            int mid = left + ((right - left) >> 1);
            if (num / mid <= mid) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return left * left == num;
    }
};

Go

func isPerfectSquare(num int) bool {
	left, right := 1, num
	for left < right {
		mid := left + (right-left)>>1
		if num/mid <= mid {
			right = mid
		} else {
			left = mid + 1
		}
	}
	return left*left == num
}

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