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
1 public class Solution { 2 public boolean isPerfectSquare(int num) { 3 int low = 1, high = num; 4 5 while (low <= high) { 6 int mid = low + (high - low) / 2; 7 8 if (mid == num / mid && num % mid == 0) return true; 9 else if (mid > num / mid) high = mid - 1; 10 else low = mid + 1; 11 } 12 return false; 13 } 14 }
原文：http://www.cnblogs.com/amazingzoe/p/6391424.html