"""
69. Sqrt(x)
Implement int sqrt(int x).
Compute and return the square root of x, where x is guaranteed to 
be a non-negative integer.
Since the return type is an integer, the decimal digits are 
truncated and only the integer part of the result is returned.

Example 1:
Input: 4
Output: 2

Example 2:
Input: 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since the 
decimal part is truncated, 2 is returned.
"""
class Solution(object):
    def mySqrt(self, x):
        l, r = 0, x
        while l <= r:
            mid = l + (r-l)//2
            if mid * mid <= x < (mid+1)*(mid+1):
                return mid
            elif x < mid * mid:
                r = mid
            else:
                l = mid + 1        