367. Valid Perfect Square

Given a positive integer num, write a function which returns True if num is a perfect square else False.

Code:

class Solution {
    public boolean isPerfectSquare(int num) {
        long r = num;
        while (r * r > num) {
            r = (r + num / r) / 2;
        }
        return r * r == num;
    }
}

---

解题思路

• 使用Newton’s Method解决平方根问题。