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

class Solution:
    def isPerfectSquare(self, num: int) -> bool:
        i = 1
        while num > 0:
            num -= i
            i += 2
        return num == 0

Java

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

class Solution {
    public boolean isPerfectSquare(int num) {
        for (int i = 1; num > 0; i += 2) {
            num -= i;
        }
        return num == 0;
    }
}

C++

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

class Solution {
public:
    bool isPerfectSquare(int num) {
        for (int i = 1; num > 0; i += 2) num -= i;
        return num == 0;
    }
};

Go

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

func isPerfectSquare(num int) bool {
	for i := 1; num > 0; i += 2 {
		num -= i
	}
	return num == 0
}

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