diff --git a/src/main/java/com/thealgorithms/others/MaximumSlidingWindow.java b/src/main/java/com/thealgorithms/others/MaximumSlidingWindow.java new file mode 100644 index 000000000..d0b2c2a0e --- /dev/null +++ b/src/main/java/com/thealgorithms/others/MaximumSlidingWindow.java @@ -0,0 +1,56 @@ +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 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 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; + } +} diff --git a/src/test/java/com/thealgorithms/others/MaximumSlidingWindowTest.java b/src/test/java/com/thealgorithms/others/MaximumSlidingWindowTest.java new file mode 100644 index 000000000..9209136a5 --- /dev/null +++ b/src/test/java/com/thealgorithms/others/MaximumSlidingWindowTest.java @@ -0,0 +1,63 @@ +package com.thealgorithms.others; + +import static org.junit.jupiter.api.Assertions.assertArrayEquals; + +import org.junit.jupiter.api.BeforeEach; +import org.junit.jupiter.api.Test; + +class MaximumSlidingWindowTest { + + MaximumSlidingWindow msw; + int[] nums; + int k; + + @BeforeEach + void setUp() { + msw = new MaximumSlidingWindow(); // Initialize the MaximumSlidingWindow object + } + + // Test for a simple sliding window case + @Test + void testMaxSlidingWindowSimpleCase() { + nums = new int[] {1, 3, -1, -3, 5, 3, 6, 7}; + k = 3; + int[] expected = {3, 3, 5, 5, 6, 7}; + assertArrayEquals(expected, msw.maxSlidingWindow(nums, k)); + } + + // Test when window size is 1 (output should be the array itself) + @Test + void testMaxSlidingWindowWindowSizeOne() { + nums = new int[] {4, 2, 12, 11, -5}; + k = 1; + int[] expected = {4, 2, 12, 11, -5}; + assertArrayEquals(expected, msw.maxSlidingWindow(nums, k)); + } + + // Test when the window size is equal to the array length (output should be a single max element) + @Test + void testMaxSlidingWindowWindowSizeEqualsArrayLength() { + nums = new int[] {4, 2, 12, 11, -5}; + k = nums.length; + int[] expected = {12}; // Maximum of the entire array + assertArrayEquals(expected, msw.maxSlidingWindow(nums, k)); + } + + // Test when the input array is empty + @Test + void testMaxSlidingWindowEmptyArray() { + nums = new int[] {}; + k = 3; + int[] expected = {}; + assertArrayEquals(expected, msw.maxSlidingWindow(nums, k)); + } + + // Test when the window size is larger than the array (should return empty) + @Test + void testMaxSlidingWindowWindowSizeLargerThanArray() { + nums = new int[] {1, 2, 3}; + k = 5; + int[] expected = {}; // Window size is too large, so no result + assertArrayEquals(expected, msw.maxSlidingWindow(nums, k)); + } +}