July 5th 2023

Problem Description permalink

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.

Solution permalink

/**
 * Forward declaration of guess API.
 * @param {number} num   your guess
 * @return 	     -1 if num is higher than the picked number
 *			      1 if num is lower than the picked number
 *               otherwise return 0
 * var guess = function(num) {}
 */


function guessNumber(n: number): number {
    if (n == 1){
        return 1
    }

    let lowerBound = 0;
    let upperBound = n;

    let guessNum = lowerBound + Math.floor((upperBound - lowerBound) / 2)
    let guessResult = guess(guessNum);

    while (lowerBound >= 0 && upperBound <= n ){
        if (guessResult === -1){
            upperBound = guessNum - 1;
        } else if (guessResult == 1){
            lowerBound = guessNum + 1
        } else {
            return guessNum
        }

        guessNum = lowerBound + Math.floor((upperBound - lowerBound) / 2)
        guessResult = guess(guessNum);
    }

    return 0
};

Discussion permalink