0367-valid-perfect-square.js

/**
 * 367. Valid Perfect Square
 * https://leetcode.com/problems/valid-perfect-square/
 * Difficulty: Easy
 *
 * 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.
 */

/**
 * @param {number} num
 * @return {boolean}
 */
var isPerfectSquare = function(num) {
  let i = 1;

  while (num > 0) {
    num -= i;
    i += 2;
    if (num === 0) {
      return true;
    }
  }

  return false;
};