牛顿法

用牛顿法求平方根，早有耳闻

class Solution(object):

def mySqrt(self, x):

def diedai(x0,a):

return (x0*x0+a)/2/x0

x0=a=float(x)

if x==0:

return 0

while int(x0)!=int(diedai(x0,a)):

x0=diedai(x0,a)

return int(x0)