Leetcode 367. Valid Perfect Square (Medium) (cpp)

Leetcode 367. Valid Perfect Square (Medium) (cpp)

Tag: Binary Search, Math

Difficulty: Medium

/*367. Valid Perfect Square (Medium)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: 16Returns: TrueExample 2:Input: 14Returns: False*/class Solution {public:bool isPerfectSquare(int num) {int l = 1, r = num;while (l < r - 1) {int mid = (l + r) / 2;if (mid * mid == num) return true;else if (mid > num / mid) r = mid;else l = mid;}if ((l * l == num) || (r * r == num))  return true;return false;}};