367 valid perfect square
367. Valid Perfect Square
题目:
https://leetcode.com/problems/valid-perfect-square/
难度:
Medium
直接用循环做也可以AC
class Solution(object):
def isPerfectSquare(self, num):
"""
:type num: int
:rtype: bool
"""
if num == 1 or num == 4 : return True
for i in xrange(num//2):
if i*i == num:
return True
elif i*i > num:
return False
return False
然后发现有传说中的牛顿法
有待阅读，然后还有二分法
r = x
while r*r > x:
r = (r + x/r) / 2
return r*r == x
