SlidingWindowMaximum.java

// Sliding window maximum problem
import java.util.*;

public class SlidingWindowMaximum {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter number of elements: ");
        int n = sc.nextInt();

        int[] nums = new int[n];
        System.out.println("Enter array elements:");
        for (int i = 0; i < n; i++) {
            nums[i] = sc.nextInt();
        }
        System.out.print("Enter window size k: ");
        int k = sc.nextInt();

        int[] result = maxSlidingWindow(nums, k);

        System.out.println("Maximum of each sliding window:");
        for (int val : result) {
            System.out.print(val + " ");
        }
    }

    public static int[] maxSlidingWindow(int[] nums, int k) {
        if (nums.length == 0 || k <= 0) return new int[0];

        int n = nums.length;
        int[] result = new int[n - k + 1];
        Deque<Integer> deque = new LinkedList<>();

        for (int i = 0; i < n; i++) {
            while (!deque.isEmpty() && deque.peekFirst() < i - k + 1) {
                deque.pollFirst();
            }
            while (!deque.isEmpty() && nums[deque.peekLast()] < nums[i]) {
                deque.pollLast();
            }
            deque.offerLast(i);
            if (i >= k - 1) {
                result[i - k + 1] = nums[deque.peekFirst()];
            }
        }

        return result;
    }
}