Add BinaryTreePaths algorithm with user input example

Author: konduri-lakshmi-prasanna

src/main/java/com/thealgorithms/backtracking/BinaryTreePaths.java

@@ -0,0 +1,75 @@
+package com.thealgorithms.backtracking;
+import java.util.*;
+public class BinaryTreePaths {
+    static class TreeNode {
+        int val;
+        TreeNode left;
+        TreeNode right;
+
+        TreeNode(int val) {
+            this.val = val;
+        }
+    }
+    public List<String> binaryTreePaths(TreeNode root) {
+        List<String> list = new ArrayList<>();
+        if (root == null) return list;
+        dfs(root, "", list);
+        return list;
+    }
+
+    private void dfs(TreeNode node, String path, List<String> list) {
+        if (node == null) return;
+
+        if (path.isEmpty()) path = "" + node.val;
+        else path += "->" + node.val;
+
+        if (node.left == null && node.right == null) {
+            list.add(path);
+            return;
+        }
+
+        dfs(node.left, path, list);
+        dfs(node.right, path, list);
+    }
+    private static TreeNode buildTreeFromInput(Scanner sc) {
+        System.out.print("Enter number of nodes: ");
+        int n = sc.nextInt();
+        if (n == 0) return null;
+
+        System.out.println("Enter node values in level order (use -1 for nulls):");
+        int[] values = new int[n];
+        for (int i = 0; i < n; i++) values[i] = sc.nextInt();
+
+        if (values[0] == -1) return null;
+        TreeNode root = new TreeNode(values[0]);
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.add(root);
+
+        int i = 1;
+        while (i < n && !queue.isEmpty()) {
+            TreeNode current = queue.poll();
+            if (i < n && values[i] != -1) {
+                current.left = new TreeNode(values[i]);
+                queue.add(current.left);
+            }
+            i++;
+            if (i < n && values[i] != -1) {
+                current.right = new TreeNode(values[i]);
+                queue.add(current.right);
+            }
+            i++;
+        }
+        return root;
+    }
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        TreeNode root = buildTreeFromInput(sc);
+
+        BinaryTreePaths solver = new BinaryTreePaths();
+        List<String> result = solver.binaryTreePaths(root);
+
+        System.out.println("All root-to-leaf paths: " + result);
+        sc.close();
+    }
+}