239. Sliding Window Maximum

Description

You are given an array of integers nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position.

Return the max sliding window.

 

Example 1:

Input: nums = [1,3,-1,-3,5,3,6,7], k = 3
Output: [3,3,5,5,6,7]
Explanation: 
Window position                Max
---------------               -----
[1  3  -1] -3  5  3  6  7       3
 1 [3  -1  -3] 5  3  6  7       3
 1  3 [-1  -3  5] 3  6  7       5
 1  3  -1 [-3  5  3] 6  7       5
 1  3  -1  -3 [5  3  6] 7       6
 1  3  -1  -3  5 [3  6  7]      7

Example 2:

Input: nums = [1], k = 1
Output: [1]

 

Constraints:

• 1 <= nums.length <= 105
• -104 <= nums[i] <= 104
• 1 <= k <= nums.length

 

Solutions

Solution: Monotonic Queue

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

 

JavaScript

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number[]}
 */
const maxSlidingWindow = function (nums, k) {
  const deque = [];
  const result = [];

  for (let index = 0; index < nums.length; index++) {
    const num = nums[index];

    if (deque.length && deque[0] === index - k) {
      deque.shift();
    }
    while (deque.length && nums[deque.at(-1)] <= num) {
      deque.pop();
    }
    deque.push(index);
    if (index + 1 < k) continue;
    result.push(nums[deque[0]]);
  }
  return result;
};