Add Longest Subarray With Sum Less Than or Equal to K algorithm (#6042)

Author: Chiefpatwal

src/main/java/com/thealgorithms/datastructures/trees/BinaryTree.java

@@ -144,7 +144,7 @@ public boolean remove(int value) {
             if (temp == root) {
                 root = null;
             } // This if/else assigns the new node to be either the left or right child of the
-              // parent
+            // parent
             else if (temp.parent.data < temp.data) {
                 temp.parent.right = null;
             } else {

src/main/java/com/thealgorithms/slidingwindow/LongestSubarrayWithSumLessOrEqualToK.java

@@ -0,0 +1,48 @@
+package com.thealgorithms.slidingwindow;
+
+/**
+ * The Longest Subarray with Sum Less Than or Equal to k algorithm finds the length
+ * of the longest subarray whose sum is less than or equal to a given value k.
+ *
+ * <p>
+ * Worst-case performance O(n)
+ * Best-case performance O(n)
+ * Average performance O(n)
+ * Worst-case space complexity O(1)
+ *
+ * @author https://github.com/Chiefpatwal
+ */
+public final class LongestSubarrayWithSumLessOrEqualToK {
+
+    // Prevent instantiation
+    private LongestSubarrayWithSumLessOrEqualToK() {
+    }
+
+    /**
+     * This method finds the length of the longest subarray with a sum less than or equal to k.
+     *
+     * @param arr is the input array
+     * @param k   is the maximum sum allowed
+     * @return the length of the longest subarray with sum less than or equal to k
+     */
+    public static int longestSubarrayWithSumLEK(int[] arr, int k) {
+        int maxLength = 0; // To store the maximum length found
+        int currentSum = 0; // To store the current sum of the window
+        int left = 0; // Left index of the sliding window
+
+        for (int right = 0; right < arr.length; right++) {
+            currentSum += arr[right]; // Expand the window to the right
+
+            // Shrink the window from the left if the current sum exceeds k
+            while (currentSum > k && left <= right) {
+                currentSum -= arr[left]; // Remove the leftmost element
+                left++; // Move the left index to the right
+            }
+
+            // Update maxLength if the current window is valid
+            maxLength = Math.max(maxLength, right - left + 1);
+        }
+
+        return maxLength; // Return the maximum length found
+    }
+}

src/test/java/com/thealgorithms/datastructures/trees/BinaryTreeTest.java

@@ -1,82 +1,78 @@
 package com.thealgorithms.datastructures.trees;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.fail;
-
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
+/**
+ * Unit tests for the BinaryTree class.
+ */
 public class BinaryTreeTest {
 
-    // checks that adding populating the tree and searching for data
-    // retrieves the expected data
     @Test
-    void test1() {
-        BinaryTree t = new BinaryTree();
-        t.put(3);
-        t.put(5);
-        t.put(7);
-        t.put(9);
-        t.put(12);
+    public void testInsertAndFind() {
+        BinaryTree tree = new BinaryTree();
+        tree.put(3);
+        tree.put(5);
+        tree.put(7);
+        tree.put(9);
+        tree.put(12);
 
-        assertEquals(t.find(5).data, 5);
-        assertEquals(t.find(7).data, 7);
+        Assertions.assertNotNull(tree.find(5), "Node with value 5 should exist");
+        Assertions.assertEquals(5, tree.find(5).data, "Value of the found node should be 5");
+        Assertions.assertEquals(7, tree.find(7).data, "Value of the found node should be 7");
     }
 
-    // checks that removing data from the tree
-    // properly removes and makes the new root the expected new root
     @Test
-    void test2() {
-        BinaryTree t = new BinaryTree();
-        t.put(3);
-        t.put(5);
-        t.put(7);
-        t.put(9);
-        t.put(12);
-        t.remove(3);
-        t.remove(5);
-        t.remove(7);
+    public void testRemove() {
+        BinaryTree tree = new BinaryTree();
+        tree.put(3);
+        tree.put(5);
+        tree.put(7);
+        tree.put(9);
+        tree.put(12);
+        tree.remove(3);
+        tree.remove(5);
+        tree.remove(7);
 
-        // Checks whether the root is null before accessing date
-        if (t.getRoot() != null) {
-            assertEquals(t.getRoot().data, 9);
+        Assertions.assertNotNull(tree.getRoot(), "Root should not be null after removals");
+        if (tree.getRoot() != null) {
+            Assertions.assertEquals(9, tree.getRoot().data, "Root value should be 9 after removals");
         } else {
-            fail("The root node is null after removal.");
+            Assertions.fail("Root should not be null after removals, but it is.");
         }
     }
 
-    // checks that removing an unexistend node returns false
-    //  as specified by the documentation of the function
     @Test
-    void test3() {
-        BinaryTree t = new BinaryTree();
-        t.put(3);
-        t.put(5);
-        t.put(7);
-        t.put(9);
-        t.put(12);
+    public void testRemoveReturnValue() {
+        BinaryTree tree = new BinaryTree();
+        tree.put(3);
+        tree.put(5);
+        tree.put(7);
+        tree.put(9);
+        tree.put(12);
 
-        assertEquals(t.remove(9), true);
-        assertEquals(t.remove(398745987), false);
+        Assertions.assertTrue(tree.remove(9), "Removing existing node 9 should return true");
+        Assertions.assertFalse(tree.remove(398745987), "Removing non-existing node should return false");
     }
 
-    // check if the bfs, inOrder, preOrder and postOrder functions
-    // worg as expected, also increases the coverage measures in
-    // JaCoCo
     @Test
-    void test4() {
-        BinaryTree t = new BinaryTree();
-        t.put(3);
-        t.put(5);
-        t.put(7);
-        t.put(9);
-        t.put(12);
+    public void testTraversalMethods() {
+        BinaryTree tree = new BinaryTree();
+        tree.put(3);
+        tree.put(5);
+        tree.put(7);
+        tree.put(9);
+        tree.put(12);
+
+        // Testing traversal methods
+        tree.bfs(tree.getRoot());
+        tree.inOrder(tree.getRoot());
+        tree.preOrder(tree.getRoot());
+        tree.postOrder(tree.getRoot());
 
-        t.bfs(t.find(12));
-        t.inOrder(t.getRoot());
-        t.preOrder(t.getRoot());
-        t.postOrder(t.getRoot());
+        Assertions.assertTrue(tree.remove(9), "Removing existing node 9 should return true");
+        Assertions.assertFalse(tree.remove(398745987), "Removing non-existing node should return false");
 
-        assertEquals(t.remove(9), true);
-        assertEquals(t.remove(398745987), false);
+        Assertions.assertNotNull(tree.getRoot(), "Root should not be null after operations");
     }
 }

src/test/java/com/thealgorithms/slidingwindow/LongestSubarrayWithSumLessOrEqualToKTest.java

@@ -0,0 +1,22 @@
+package com.thealgorithms.slidingwindow;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for the LongestSubarrayWithSumLessOrEqualToK algorithm.
+ */
+public class LongestSubarrayWithSumLessOrEqualToKTest {
+
+    /**
+     * Tests for the longest subarray with a sum less than or equal to k.
+     */
+    @Test
+    public void testLongestSubarrayWithSumLEK() {
+        assertEquals(3, LongestSubarrayWithSumLessOrEqualToK.longestSubarrayWithSumLEK(new int[] {1, 2, 3, 4}, 6)); // {1, 2, 3}
+        assertEquals(4, LongestSubarrayWithSumLessOrEqualToK.longestSubarrayWithSumLEK(new int[] {1, 2, 3, 4}, 10)); // {1, 2, 3, 4}
+        assertEquals(2, LongestSubarrayWithSumLessOrEqualToK.longestSubarrayWithSumLEK(new int[] {5, 1, 2, 3}, 5)); // {5}
+        assertEquals(0, LongestSubarrayWithSumLessOrEqualToK.longestSubarrayWithSumLEK(new int[] {1, 2, 3}, 0)); // No valid subarray
+    }
+}