Add Right View of Binary Tree algorithm (DFS + BFS)

Author: Mahadevan2005

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

@@ -0,0 +1,92 @@
+package com.thealgorithms.datastructures.trees;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+/**
+ * The Right View of a Binary Tree is the set of nodes visible when the tree
+ * is viewed from the right side. For each level, the rightmost node is part
+ * of the right view.
+ *
+ * <p>This implementation provides both DFS and BFS approaches.</p>
+ */
+public class RightViewOfBinaryTree {
+
+    /**
+     * Node class structure. If the repository already has a standard Node class,
+     * reuse it instead of redefining this one.
+     */
+    static class Node {
+        int data;
+        Node left;
+        Node right;
+
+        Node(int data) {
+            this.data = data;
+            left = right = null;
+        }
+    }
+
+    /**
+     * Returns the right view of the binary tree using DFS.
+     *
+     * @param root the root of the binary tree
+     * @return list of node values visible from the right
+     */
+    public static List<Integer> rightViewDFS(Node root) {
+        List<Integer> result = new ArrayList<>();
+        dfsHelper(root, 0, result);
+        return result;
+    }
+
+    private static void dfsHelper(Node node, int level, List<Integer> result) {
+        if (node == null) return;
+        if (level == result.size()) {
+            result.add(node.data);
+        }
+        dfsHelper(node.right, level + 1, result);
+        dfsHelper(node.left, level + 1, result);
+    }
+
+    /**
+     * Returns the right view using a level-order (BFS) approach.
+     *
+     * @param root the root node
+     * @return list of right view nodes
+     */
+    public static List<Integer> rightViewBFS(Node root) {
+        List<Integer> result = new ArrayList<>();
+        if (root == null) return result;
+
+        Queue<Node> queue = new LinkedList<>();
+        queue.offer(root);
+
+        while (!queue.isEmpty()) {
+            int size = queue.size();
+            for (int i = 0; i < size; i++) {
+                Node current = queue.poll();
+                if (i == size - 1) {
+                    result.add(current.data);
+                }
+                if (current.left != null) queue.offer(current.left);
+                if (current.right != null) queue.offer(current.right);
+            }
+        }
+        return result;
+    }
+
+    // Example usage
+    public static void main(String[] args) {
+        Node root = new Node(1);
+        root.left = new Node(2);
+        root.right = new Node(3);
+        root.left.left = new Node(4);
+        root.left.right = new Node(5);
+        root.right.right = new Node(6);
+
+        System.out.println("Right View (DFS): " + rightViewDFS(root));
+        System.out.println("Right View (BFS): " + rightViewBFS(root));
+    }
+}

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

@@ -0,0 +1,41 @@
+package com.thealgorithms.datastructures.trees;
+
+import org.junit.jupiter.api.Test;
+import java.util.List;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class RightViewOfBinaryTreeTest {
+
+    @Test
+    public void testRightViewOfBalancedTree() {
+        RightViewOfBinaryTree.Node root = new RightViewOfBinaryTree.Node(1);
+        root.left = new RightViewOfBinaryTree.Node(2);
+        root.right = new RightViewOfBinaryTree.Node(3);
+        root.left.left = new RightViewOfBinaryTree.Node(4);
+        root.left.right = new RightViewOfBinaryTree.Node(5);
+        root.right.right = new RightViewOfBinaryTree.Node(6);
+
+        List<Integer> expected = List.of(1, 3, 6);
+        assertEquals(expected, RightViewOfBinaryTree.rightViewDFS(root));
+    }
+
+    @Test
+    public void testRightSkewedTree() {
+        RightViewOfBinaryTree.Node root = new RightViewOfBinaryTree.Node(1);
+        root.right = new RightViewOfBinaryTree.Node(2);
+        root.right.right = new RightViewOfBinaryTree.Node(3);
+
+        List<Integer> expected = List.of(1, 2, 3);
+        assertEquals(expected, RightViewOfBinaryTree.rightViewDFS(root));
+    }
+
+    @Test
+    public void testLeftSkewedTree() {
+        RightViewOfBinaryTree.Node root = new RightViewOfBinaryTree.Node(1);
+        root.left = new RightViewOfBinaryTree.Node(2);
+        root.left.left = new RightViewOfBinaryTree.Node(3);
+
+        List<Integer> expected = List.of(1, 2, 3);
+        assertEquals(expected, RightViewOfBinaryTree.rightViewBFS(root));
+    }
+}