69. x 的平方根
#平方根的值一定在1,x之间,是一个有序数组
#那么就满足二分查找的条件
class Solution:
def mySqrt(self, x: int) -> int:
if x==0 or x==1:
return x #0和1的算术平方根为1
low,high,res = 1,x,-1 #初始化
while low<=high:
mid = (low+high)//2
if mid*mid<=x:
res = mid
low=mid+1
else:
high=mid-1
return res