[leetcode] 374. Guess Number Higher or Lower _ Algorithm Problem Solve for python

1. Problem

374. 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 will tell you whether the number I picked is higher or lower than your guess.

You call a pre-defined API int guess(int num), which returns three possible results:

• -1: Your guess is higher than the number I picked (i.e. num > pick).
• 1: Your guess is lower than the number I picked (i.e. num < pick).
• 0: your guess is equal to the number I picked (i.e. num == pick). Return the number that I picked.

Example 1:

Input: n = 10, pick = 6
Output: 6

Example 2:

Input: n = 1, pick = 1
Output: 1

Example 3:

Input: n = 2, pick = 1
Output: 1

Constraints:

• 1 <= n <= 231 - 1
• 1 <= pick <= n

2. Solution

I solved this problem like this.

Using binary search logic, we can solve this problem so easily.

class Solution:
    def guessNumber(self, n: int) -> int:
        left, right = 1, n
        while left <= right:
            mid = (left + right) // 2
            if guess(mid) == 0:
                return mid
            elif guess(mid) == -1:
                right = mid - 1
            else:
                left = mid + 1

        return -1