LeetCode in Kotlin

239. Sliding Window Maximum

Hard

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

Solution

import java.util.LinkedList

class Solution {
    fun maxSlidingWindow(nums: IntArray, k: Int): IntArray {
        val n = nums.size
        val res = IntArray(n - k + 1)
        var x = 0
        val dq = LinkedList<Int>()
        var i = 0
        var j = 0
        while (j < nums.size) {
            while (dq.isNotEmpty() && dq.peekLast() < nums[j]) {
                dq.pollLast()
            }
            dq.addLast(nums[j])
            if (j - i + 1 == k) {
                res[x] = dq.peekFirst()
                ++x
                if (dq.peekFirst() == nums[i]) {
                    dq.pollFirst()
                }
                ++i
            }
            ++j
        }
        return res
    }
}

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