# Sliding Window: 239. Sliding Window Maximum

Leetcode #:239Name:Sliding Window MaximumDifficulty:HardUrl:https://leetcode.com/problems/sliding-window-maximum/

# Problem Statement

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

`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

Constraints

`1 <= nums.length <= 105`

`104 <= nums[i] <= 104`

`1 <= k <= nums.length`

# Approach

Brute Force: O(k * (n — k))

We can simply take the maximum of each sliding window of size k as we shift it by 1 until we scan the given array from left to right. The time complexity of this would be the size of the sliding window (k) * the number of sliding windows we are going to have (n — k).

Monotonically Decreasing Queue: O(n)

If we have a sliding window and we see a value that is greater than previous values in our window, then we can eliminate those previous values from our window.

# Code

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