Merge branch 'master' into patch-1

Author: preritasaini1

DIRECTORY.md

@@ -912,6 +912,7 @@
               * [StackArrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/StackArrayTest.java)
               * [StackOfLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/stacks/StackOfLinkedListTest.java)
             * trees
+              * [AVLTreeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/AVLTreeTest.java)
               * [BinaryTreeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/BinaryTreeTest.java)
               * [BoundaryTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/BoundaryTraversalTest.java)
               * [BSTFromSortedArrayTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/BSTFromSortedArrayTest.java)

src/main/java/com/thealgorithms/bitmanipulation/SwapAdjacentBits.java

@@ -1,14 +1,45 @@
 package com.thealgorithms.bitmanipulation;
 
 /**
- * Swap every pair of adjacent bits of a given number.
- * @author Lakshyajeet Singh Goyal (https://github.com/DarkMatter-999)
+ * A utility class to swap every pair of adjacent bits in a given integer.
+ * This operation shifts the even-positioned bits to odd positions and vice versa.
+ *
+ * Example:
+ * - Input: 2 (binary: `10`) → Output: 1 (binary: `01`)
+ * - Input: 43 (binary: `101011`) → Output: 23 (binary: `010111`)
+ *
+ * **Explanation of the Algorithm:**
+ * 1. Mask even-positioned bits: Using `0xAAAAAAAA` (binary: `101010...`),
+ *    which selects bits in even positions.
+ * 2. Mask odd-positioned bits: Using `0x55555555` (binary: `010101...`),
+ *    which selects bits in odd positions.
+ * 3. Shift bits:
+ *    - Right-shift even-positioned bits by 1 to move them to odd positions.
+ *    - Left-shift odd-positioned bits by 1 to move them to even positions.
+ * 4. Combine both shifted results using bitwise OR (`|`) to produce the final result.
+ *
+ * Use Case: This algorithm can be useful in applications involving low-level bit manipulation,
+ * such as encoding, data compression, or cryptographic transformations.
+ *
+ * Time Complexity: O(1) (constant time, since operations are bitwise).
+ *
+ * Author: Lakshyajeet Singh Goyal (https://github.com/DarkMatter-999)
  */
-
 public final class SwapAdjacentBits {
     private SwapAdjacentBits() {
     }
 
+    /**
+     * Swaps every pair of adjacent bits of a given integer.
+     * Steps:
+     * 1. Mask the even-positioned bits.
+     * 2. Mask the odd-positioned bits.
+     * 3. Shift the even bits to the right and the odd bits to the left.
+     * 4. Combine the shifted bits.
+     *
+     * @param num the integer whose bits are to be swapped
+     * @return the integer after swapping every pair of adjacent bits
+     */
     public static int swapAdjacentBits(int num) {
         // mask the even bits (0xAAAAAAAA => 10101010...)
         int evenBits = num & 0xAAAAAAAA;

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

@@ -1,11 +1,19 @@
 package com.thealgorithms.datastructures.trees;
 
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Represents an AVL Tree, a self-balancing binary search tree.
+ * In an AVL tree, the heights of the two child subtrees of any node
+ * differ by at most one. If they differ by more than one at any time,
+ * rebalancing is performed to restore this property.
+ */
 public class AVLTree {
 
     private Node root;
 
-    private class Node {
-
+    private static class Node {
         private int key;
         private int balance;
         private int height;
@@ -17,8 +25,18 @@ private class Node {
             key = k;
             parent = p;
         }
+
+        public Integer getBalance() {
+            return balance;
+        }
     }
 
+    /**
+     * Inserts a new key into the AVL tree.
+     *
+     * @param key the key to be inserted
+     * @return {@code true} if the key was inserted, {@code false} if the key already exists
+     */
     public boolean insert(int key) {
         if (root == null) {
             root = new Node(key, null);
@@ -31,7 +49,6 @@ public boolean insert(int key) {
                 }
 
                 parent = n;
-
                 boolean goLeft = n.key > key;
                 n = goLeft ? n.left : n.right;
 
@@ -49,8 +66,32 @@ public boolean insert(int key) {
         return true;
     }
 
+    /**
+     * Deletes a key from the AVL tree.
+     *
+     * @param delKey the key to be deleted
+     */
+    public void delete(int delKey) {
+        if (root == null) {
+            return;
+        }
+
+        // Find the node to be deleted
+        Node node = root;
+        Node child = root;
+        while (child != null) {
+            node = child;
+            child = delKey >= node.key ? node.right : node.left;
+            if (delKey == node.key) {
+                delete(node);
+                return;
+            }
+        }
+    }
+
     private void delete(Node node) {
         if (node.left == null && node.right == null) {
+            // Leaf node
             if (node.parent == null) {
                 root = null;
             } else {
@@ -64,6 +105,8 @@ private void delete(Node node) {
             }
             return;
         }
+
+        // Node has one or two children
         Node child;
         if (node.left != null) {
             child = node.left;
@@ -80,26 +123,49 @@ private void delete(Node node) {
         delete(child);
     }
 
-    public void delete(int delKey) {
-        if (root == null) {
-            return;
+    /**
+     * Returns a list of balance factors for each node in the tree.
+     *
+     * @return a list of integers representing the balance factors of the nodes
+     */
+    public List<Integer> returnBalance() {
+        List<Integer> balances = new ArrayList<>();
+        returnBalance(root, balances);
+        return balances;
+    }
+
+    private void returnBalance(Node n, List<Integer> balances) {
+        if (n != null) {
+            returnBalance(n.left, balances);
+            balances.add(n.getBalance());
+            returnBalance(n.right, balances);
         }
-        Node node = root;
-        Node child = root;
+    }
 
-        while (child != null) {
-            node = child;
-            child = delKey >= node.key ? node.right : node.left;
-            if (delKey == node.key) {
-                delete(node);
-                return;
-            }
+    /**
+     * Searches for a key in the AVL tree.
+     *
+     * @param key the key to be searched
+     * @return true if the key is found, false otherwise
+     */
+    public boolean search(int key) {
+        Node result = searchHelper(this.root, key);
+        return result != null;
+    }
+
+    private Node searchHelper(Node root, int key) {
+        if (root == null || root.key == key) {
+            return root;
         }
+
+        if (root.key > key) {
+            return searchHelper(root.left, key);
+        }
+        return searchHelper(root.right, key);
     }
 
     private void rebalance(Node n) {
         setBalance(n);
-
         if (n.balance == -2) {
             if (height(n.left.left) >= height(n.left.right)) {
                 n = rotateRight(n);
@@ -143,7 +209,6 @@ private Node rotateLeft(Node a) {
         }
 
         setBalance(a, b);
-
         return b;
     }
 
@@ -169,7 +234,6 @@ private Node rotateRight(Node a) {
         }
 
         setBalance(a, b);
-
         return b;
     }
 
@@ -197,53 +261,9 @@ private void setBalance(Node... nodes) {
         }
     }
 
-    public void printBalance() {
-        printBalance(root);
-    }
-
-    private void printBalance(Node n) {
-        if (n != null) {
-            printBalance(n.left);
-            System.out.printf("%s ", n.balance);
-            printBalance(n.right);
-        }
-    }
-
     private void reheight(Node node) {
         if (node != null) {
             node.height = 1 + Math.max(height(node.left), height(node.right));
         }
     }
-
-    public boolean search(int key) {
-        Node result = searchHelper(this.root, key);
-        return result != null;
-    }
-
-    private Node searchHelper(Node root, int key) {
-        // root is null or key is present at root
-        if (root == null || root.key == key) {
-            return root;
-        }
-
-        // key is greater than root's key
-        if (root.key > key) {
-            return searchHelper(root.left, key); // call the function on the node's left child
-        }
-        // key is less than root's key then
-        // call the function on the node's right child as it is greater
-        return searchHelper(root.right, key);
-    }
-
-    public static void main(String[] args) {
-        AVLTree tree = new AVLTree();
-
-        System.out.println("Inserting values 1 to 10");
-        for (int i = 1; i < 10; i++) {
-            tree.insert(i);
-        }
-
-        System.out.print("Printing balance: ");
-        tree.printBalance();
-    }
 }

src/test/java/com/thealgorithms/bitmanipulation/SwapAdjacentBitsTest.java

@@ -8,13 +8,20 @@
 class SwapAdjacentBitsTest {
 
     @ParameterizedTest
-    @CsvSource({
-        "2, 1", // 2 (10 in binary) should become 1 (01 in binary)
-        "43, 23", // 43 should become 23
-        "153, 102", // 153 should become 102
-        "15, 15", // 15 (1111) remains 15 (1111)
-        "0, 0" // 0 (0000) remains 0 (0000)
-    })
+    @CsvSource({"2, 1", // 2 (binary: 10) -> 1 (binary: 01)
+        "43, 23", // 43 (binary: 101011) -> 23 (binary: 010111)
+        "153, 102", // 153 (binary: 10011001) -> 102 (binary: 01100110)
+        "15, 15", // 15 (binary: 1111) -> 15 (binary: 1111) (no change)
+        "0, 0", // 0 (binary: 0000) -> 0 (binary: 0000) (no change)
+        "1, 2", // 1 (binary: 01) -> 2 (binary: 10)
+        "170, 85", // 170 (binary: 10101010) -> 85 (binary: 01010101)
+        "85, 170", // 85 (binary: 01010101) -> 170 (binary: 10101010)
+        "255, 255", // 255 (binary: 11111111) -> 255 (binary: 11111111) (no change)
+        "128, 64", // 128 (binary: 10000000) -> 64 (binary: 01000000)
+        "1024, 2048",
+        "-1, -1", // -1 (all bits 1) remains -1 (no change due to two's complement)
+        "-2, -3", // -2 (binary: ...1110) -> -3 (binary: ...1101)
+        "2147483647, -1073741825", "-2147483648, -1073741824"})
     void
     testSwapAdjacentBits(int input, int expected) {
         assertEquals(expected, SwapAdjacentBits.swapAdjacentBits(input));