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
本题可以用binary search。
class Solution(object): def isPerfectSquare(self, num): """ :type num: int :rtype: bool """ low, high = 1, num while low <= high: mid = (high + low)//2 if mid**2 == num: return True elif mid**2 > num: high = mid - 1 else: low = mid + 1 return False
Leetcode 367. Valid Perfect Square
原文：http://www.cnblogs.com/lettuan/p/6228096.html