Leetcode•Apr 02, 2025
367 Valid Perfect Square
Hazrat Ali
Leetcode
Given a positive integer num, return true if num is a perfect square or false otherwise.
A perfect square is an integer that is the square of an integer. In other words, it is the product of some integer with itself.
You must not use any built-in library function, such as sqrt.
Example 1:
Input: num = 16 Output: true Explanation: We return true because 4 * 4 = 16 and 4 is an integer.
Example 2:
Input: num = 14 Output: false Explanation: We return false because 3.742 * 3.742 = 14 and 3.742 is not an integer.
* Valid Perfect Square
*
* Given a positive integer num, write a function which returns True if num is a perfect square else False.
*
* Note: Do not use any built-in library function such as sqrt.
*
* Example 1:
*
* Input: 16
* Output: true
* Example 2:
*
* Input: 14
* Output: false
Solution
/**
* @param {number} num
* @return {boolean}
*/
const isPerfectSquare = num => {
let lo = 0;
let hi = num;
while (lo <= hi) {
const mid = (lo + hi) >>> 1;
if (mid * mid === num) {
return true;
} else if (mid * mid < num) {
lo = mid + 1;
} else {
hi = mid - 1;
}
}
return false;
};