Sliding Window Maximum

class Solution {
    class MonotonicQueue {
        Deque<Integer> queue;

        public MonotonicQueue() {
             queue = new ArrayDeque<>();
        }

        public void push(int a) {
            while(!queue.isEmpty() && queue.peekLast() < a) {
                queue.pollLast();
            }
            queue.offerLast(a);
        }

        public void pop(int a) {
            if(a == queue.peekFirst()) queue.pollFirst();
        }

        public int max() {
            return queue.peekFirst();
        }
    }

    public int[] maxSlidingWindow(int[] nums, int k) {
        int[] result = new int[nums.length - k + 1];

        MonotonicQueue mq = new MonotonicQueue();
        for(int i = 0; i < nums.length; i++) {
            mq.push(nums[i]);
            if(i >= k - 1) {
                result[i - k + 1] = mq.max();
                mq.pop(nums[i-k+1]);
            }
        }
        return result;
    }
}