Given a non-negative integer x, return the square root of x rounded down to the nearest integer. The returned integer should be non-negative as well.
You must not use any built-in exponent function or operator.
For example, do not use pow(x, 0.5) in c++ or x ** 0.5 in python.
Solution:
class Solution(object):
def mySqrt(self, x):
l, r, ans = 0, x, -1
while l <= r:
mid = (l + r) // 2
if mid ** 2 <= x:
ans = mid
l = mid + 1
else:
r = mid - 1
return ans