[Data Structure] Sliding Window

Problems:

• 239. Sliding Window Maximum: https://leetcode.com/problems/sliding-window-maximum/description/
• 480. Sliding Window Median: https://leetcode.com/problems/sliding-window-median/description/

239. Sliding Window Maximum:

class Solution {
    public int[] maxSlidingWindow(int[] nums, int k) {
        if (nums == null || k == 0) {
            return new int[0];
        }
        int[] maxSlidingWindow = new int[nums.length - k + 1];
        int maxSlidingWindowPos = 0;
        Deque<Integer> potential = new ArrayDeque<>();
        for (int i = 0; i < nums.length; i++) {
            while (!potential.isEmpty() && potential.peekFirst() < i - k + 1) {
                potential.pollFirst();
            }
            
            while (!potential.isEmpty() && nums[potential.peekLast()] < nums[i]) {
                potential.pollLast();
            }
            
            potential.offer(i);
            
            if (i - k + 1 >= 0) {
                maxSlidingWindow[maxSlidingWindowPos++] = nums[potential.peekFirst()];
            }
        }
        return maxSlidingWindow;
    }
}