374. Guess Number Higher or Lower (javascript solution)

Description:

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 3 possible results:

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

Solution:

Time Complexity : O(nlog(n))
Space Complexity: O(1)

var guessNumber = function(n) {
    let left = 1, right = n

    while(left < right) {
        const mid = left + Math.floor((right-left)/2)
        const current = guess(mid)
        if(current === 0) return mid
        if(current === -1) right = mid
        else left = mid+1
    }
    return left
};