Guess the Number Higher or Lower

In this task, I worked on finding a hidden number within a given range using an efficient approach. Instead of checking every number one by one, I used binary search to reduce the number of guesses.

What I Did

I created a function guessNumber that tries to find a number between 1 and n.

There is a helper function called guess():

• It returns 0 if the guess is correct
• It returns -1 if the guessed number is too high
• It returns 1 if the guessed number is too low

How I Solved It

I used two variables:

• low starting from 1
• high starting from n

Then I repeatedly found the middle value (mid) of the range.

At each step:

• If the guess is correct, I return the number
• If the guess is too high, I move the high pointer down
• If the guess is too low, I move the low pointer up

This keeps reducing the search space until the correct number is found.

Code

class Solution:
    def guessNumber(self, n: int) -> int:
        low = 1
        high = n

        while low <= high:
            mid = (low + high) // 2
            res = guess(mid)

            if res == 0:
                return mid
            elif res == -1:
                high = mid - 1
            else:
                low = mid + 1

How It Works

The function uses binary search, which divides the range into halves each time. Instead of checking all numbers, it quickly narrows down the possible range based on the result from the guess() function.

This makes the solution much faster compared to a linear search.