【LEETCODE】374- Guess Number Higher or Lower [Python]

题目：
https://leetcode.com/problems/guess-number-higher-or-lower/

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.

分析：

It’s in the ‘easy’ class, given n, and return the number has been chosen among 1 to n, based on the feedback from the function called ‘guess’, we’ll use ‘Binary Search’ to solve it.

# 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 = 1
        right = n

        while left <= right:

            # g = left + ((right - left) >> 1)

            g = int((right+left)/2)

            if guess(g) == 1:
                left = g+1

            elif guess(g) == -1:
                right = g-1
            else:
                return g

        return left