Added dsa code

src/main/java/com/thealgorithms/datastructures/BinaryTreeRightSideView.java

@@ -0,0 +1,65 @@
+package com.thealgorithms.datastructures;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+public class BinaryTreeRightSideView {
+
+    // FIX: Make the TreeNode class static.
+    static class TreeNode {
+        int val;
+        TreeNode left, right;
+        TreeNode(int x) {
+            this.val = x;
+        }
+    }
+
+    // FIX: Make the RightSideView class static.
+    public static class RightSideView {
+        public List<Integer> rightSideView(TreeNode root) {
+            List<Integer> result = new ArrayList<>();
+            if (root == null) {
+                return result;
+            }
+
+            Queue<TreeNode> queue = new LinkedList<>();
+            queue.add(root);
+
+            while (!queue.isEmpty()) {
+                int size = queue.size();
+                for (int i = 0; i < size; i++) {
+                    TreeNode node = queue.poll();
+
+                    // If it's the last node in this level, add it to the result.
+                    if (i == size - 1) {
+                        result.add(node.val);
+                    }
+
+                    if (node.left != null) {
+                        queue.add(node.left);
+                    }
+                    if (node.right != null) {
+                        queue.add(node.right);
+                    }
+                }
+            }
+            return result;
+        }
+
+        // The main method can now correctly instantiate these static classes.
+        public static void main(String[] args) {
+            RightSideView sol = new RightSideView();
+
+            TreeNode root = new TreeNode(1);
+            root.left = new TreeNode(2);
+            root.right = new TreeNode(3);
+            root.left.right = new TreeNode(5);
+            root.right.right = new TreeNode(4);
+
+            // The logic correctly produces the right side view.
+            System.out.println(sol.rightSideView(root)); // Expected Output: [1, 3, 4]
+        }
+    }
+}