LeetCode: Guess Number Higher or Lower

Posted on November 9, 2017July 26, 2020 by braindenny

Guess number quickly

Similar Problems:

We are playing the Guess Game. The game is as follows:

I pick a number from 1 to n. You have to guess which number I picked.

Every time you guess wrong, I’ll tell you whether the number is higher or lower.

You call a pre-defined API guess(int num) which returns 3 possible results (-1, 1, or 0):

-1 : My number is lower
 1 : My number is higher
 0 : Congrats! You got it!

Example:

n = 10, I pick 6.

Return 6.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## https://code.dennyzhang.com/guess-number-higher-or-lower
## Basic Ideas: binary search
##      1 1 1 0 -1 -1 -1
## Complexity: Time O(log(n)), Space O(1)

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

class Solution(object):
    def guessNumber(self, n):
        """
        :type n: int
        :rtype: int
        """
        left, right = 1, n
        while left <= right:
            mid = int(left + (right-left)/2)
            v = guess(mid)
            if v == 0:
                return mid
            elif v == 1:
                left = mid + 1
            else:
                right = mid - 1
        return None

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