[leetcode] 367. 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
Returns: True

Example 2:

Input: 14
Returns: False

使用二分查找寻找input的开方值；

使用long long防止溢出。

我的代码如下：

class Solution {
public:bool isPerfectSquare(int num) {if (num == 1) return true;long long left = 1, mid = (num + 1) / 2, right = num;while (left <= right) {if (mid * mid == num) return true;if (mid * mid > num) right = mid - 1;else left = mid + 1;mid = (left + right) / 2;}return false;}
};

转载于:https://www.cnblogs.com/zmj97/p/7554416.html

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