LeetCode 374: Guess Number Higher or Lower Solution

Master LeetCode problem 374 (Guess Number Higher or Lower), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

374. Guess Number Higher or Lower

Easy

Binary Search Interactive

Problem Explanation

Explanation

To solve this problem, we can use a binary search algorithm. The idea is to iteratively guess the number in the middle of the range (1 to n) and adjust the search range based on the response from the guess function. If the guess is too high, we update the upper bound of the range. If the guess is too low, we update the lower bound of the range. We continue this process until we find the correct number.

Algorithm:
1. Initialize low as 1 and high as n.
2. While low is less than or equal to high, do the following:
  - Calculate the mid point as (low + high) / 2.
  - Make a guess using guess(mid).
  - Update the search range based on the guess:
    - If the guess result is -1, set high = mid - 1.
    - If the guess result is 1, set low = mid + 1.
    - If the guess result is 0, return mid.
Time Complexity: O(log n) - Binary search reduces the search space by half in every iteration.
Space Complexity: O(1) - Constant extra space is used.

Solution Code

public class Solution extends GuessGame {
    public int guessNumber(int n) {
        int low = 1;
        int high = n;
        while (low <= high) {
            int mid = low + (high - low) / 2;
            int result = guess(mid);
            if (result == 0) {
                return mid;
            } else if (result == -1) {
                high = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        return -1; // Not found
    }
}

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