LeetCode in Net

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]

Example 3:

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

Output: [1,-1]

Example 4:

Input: nums = [9,11], k = 2

Output: [11]

Example 5:

Input: nums = [4,-2], k = 2

Output: [4]

Constraints:

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

Solution

using System;
using System.Collections.Generic;

public class Solution {
    public int[] MaxSlidingWindow(int[] nums, int k) {
        int n = nums.Length;
        int[] res = new int[n - k + 1];
        int x = 0;
        LinkedList<int> dq = new LinkedList<int>();
        int i = 0;
        int j = 0;
        while (j < nums.Length) {
            while (dq.Count != 0 && dq.Last.Value < nums[j]) {
                dq.RemoveLast();
            }
            dq.AddLast(nums[j]);
            if (j - i + 1 == k) {
                res[x] = dq.First.Value;
                ++x;
                if (dq.First.Value == nums[i]) {
                    dq.RemoveFirst();
                }
                ++i;
            }
            ++j;
        }
        return res;
    }
}

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