367. Valid Perfect Square

Description

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
Returns: True

Example 2:

Input: 14
Returns: False

Solution

/**
 * Solved with binary search algorithm
 * @param {number} num
 * @return {boolean}
 */
var isPerfectSquare = function(num) {
    "use strict";
    let min = 0, max = num;
    while(min <= max) {
        let mid = min + Math.ceil((max-min)/2);
        let result = mid*mid;
        if (result === num) {
            return true;
        } else if (result > num) {
            max = mid-1;
        } else {
            min = mid+1;
        }
    }
    return false;
};