标签：solution style example else == 二分 strong isp inpu
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; } };
[leetcode] 367. Valid Perfect Square
标签：solution style example else == 二分 strong isp inpu
原文地址：http://www.cnblogs.com/zmj97/p/7554416.html
