Problem URL: Guess number higher or lower

This is a classic binary search problem. We will use binary search to find the number. We will use provided guess function to check whether the number is equal to the target or not.

# The guess API is already defined for you.
# @param num, your guess
# @return -1 if num is higher than the picked number
#          1 if num is lower than the picked number
#          otherwise return 0
# def guess(num: int) -> int:

class Solution:
    def guessNumber(self, n: int) -> int:
        l, r = 1, n
        while l <= r:
            m = (l+r)//2
            res = guess(m)
            if res == 0 :
                return m
            elif res == -1:
                r = m-1
            else:
                l = m+1

Time Complexity: O(log(n))
Space Complexity: O(1)