1535. Find the Winner of an Array Game

Problem

Given an integer array arr of distinct integers and an integer k.

A game will be played between the first two elements of the array (i.e. arr[0] and arr[1]). In each round of the game, we compare arr[0] with arr[1], the larger integer wins and remains at position 0, and the smaller integer moves to the end of the array. The game ends when an integer wins k consecutive rounds.

Return the integer which will win the game.

It is guaranteed that there will be a winner of the game.

  Example 1:

Input: arr = [2,1,3,5,4,6,7], k = 2
Output: 5
Explanation: Let's see the rounds of the game:
Round |       arr       | winner | win_count
  1   | [2,1,3,5,4,6,7] | 2      | 1
  2   | [2,3,5,4,6,7,1] | 3      | 1
  3   | [3,5,4,6,7,1,2] | 5      | 1
  4   | [5,4,6,7,1,2,3] | 5      | 2
So we can see that 4 rounds will be played and 5 is the winner because it wins 2 consecutive games.

Example 2:

Input: arr = [3,2,1], k = 10
Output: 3
Explanation: 3 will win the first 10 rounds consecutively.

  Constraints:

• 2 <= arr.length <= 105

• 1 <= arr[i] <= 106

• arr contains distinct integers.

• 1 <= k <= 109

Solution

/**
 * @param {number[]} arr
 * @param {number} k
 * @return {number}
 */
var getWinner = function(arr, k) {
    var maxIndex = 0;
    for (var i = 1; i < arr.length; i++) {
        if (arr[i] > arr[maxIndex]) maxIndex = i;
        if (i - maxIndex + (maxIndex === 0 ? 0 : 1) === k) break;
    }
    return arr[maxIndex];
};

Explain:

We keep track of the maximum number index while iterating the array, in index i, the maximum number wined i - maxIndex + 1 times (or i - maxIndex times if maxIndex is zero)

Complexity:

• Time complexity : O(n).
• Space complexity : O(1).