Add Maximum Sliding Window algorithm using deque for efficient O(n) solution

Author: pranayh24

src/main/java/com/thealgorithms/others/MaximumSlidingWindow.java

@@ -0,0 +1,68 @@
+package com.thealgorithms.others;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+/**
+ * Maximum Sliding Window Algorithm
+ *
+ * This algorithm finds the maximum element in each sliding window of size k
+ * in a given array of integers. It uses a deque (double-ended queue) to
+ * efficiently keep track of potential maximum values in the current window.
+ *
+ * Time Complexity: O(n), where n is the number of elements in the input array
+ * Space Complexity: O(k), where k is the size of the sliding window
+ */
+
+public class MaximumSlidingWindow {
+
+    /**
+     * Finds the maximum values in each sliding window of size k.
+     *
+     * @param nums The input array of integers
+     * @param windowSize The size of the sliding window
+     * @return An array of integers representing the maximums in each sliding window
+     */
+    public int[] maxSlidingWindow(int[] nums, int windowSize){
+        if(nums==null || nums.length==0 || windowSize<=0 || windowSize>nums.length) {
+            return new int[0]; // Handle edge cases
+        }
+
+        int[] result = new int[nums.length - windowSize + 1];
+        Deque<Integer> deque = new ArrayDeque<>();
+
+        for(int currentIndex=0;currentIndex<nums.length;currentIndex++){
+
+            // Remove the first element if it's outside the current window
+            if(!deque.isEmpty() && deque.peekFirst()==currentIndex-windowSize) {
+                deque.pollFirst();
+            }
+
+            // Remove all elements smaller than the current element from the end
+            while(!deque.isEmpty() && nums[deque.peekLast()]<nums[currentIndex]) {
+                deque.pollLast();
+            }
+
+            // Add the current element's index to the deque
+            deque.offerLast(currentIndex);
+
+            // If we have processed at least k elements, add to result
+            if(currentIndex>=windowSize-1) {
+                result[currentIndex - windowSize + 1] = nums[deque.peekFirst()];
+            }
+        }
+        return result;
+    }
+    public static void main(String[] args) {
+        MaximumSlidingWindow msw = new MaximumSlidingWindow();
+        int[] nums = {1,3,-1,-3,5,3,6,7};
+        int k = 3;
+
+        // Calculate the maximum sliding window
+        int[] result = msw.maxSlidingWindow(nums, k);
+
+        // Print the result
+        for(int num:result)
+            System.out.print(num+" ");
+    }
+}