[leetcode]367. Valid Perfect Square验证完全平方数

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

 

题意：

验证完全平方数

 

思路：

二分查找，可回顾之前[leetcode]278. First Bad Version首个坏版本 笔记

需要注意的是类型声明为long

 

代码：

1 class Solution { 2 public boolean isPerfectSquare(int num) { 3 long left = 0; 4 long right = num; 5 6 while (left <= right) { 7 long mid = left + (right - left) / 2; 8 if (mid * mid == num) { 9 return true; 10 } else if (mid * mid < num) { 11 left = mid + 1; 12 } else { 13 right = mid - 1; 14 } 15 } 16 return false; 17 } 18 }

 

 

转载于:https://www.cnblogs.com/liuliu5151/p/9136972.html