solves bainary tree paths

Author: anishLearnsToCode

README.md

@@ -79,7 +79,7 @@
 | 246 | [Strobogramatic Number](https://leetcode.com/problems/strobogrammatic-number) | Easy |
 | 252 | [Meeting Rooms](https://leetcode.com/problems/meeting-rooms) | Easy | |
 | 256 | [Paint House](https://leetcode.com/problems/paint-house) | Easy | |
-| 257 | [Binary Tree Paths](https://leetcode.com/problems/binary-tree-paths) | Easy | |
+| 257 | [Binary Tree Paths](https://leetcode.com/problems/binary-tree-paths) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)]() |
 | 258 | [Add Digits](https://leetcode.com/problems/add-digits) | Easy | |
 | 263 | [Ugly Number](https://leetcode.com/problems/ugly-number) | Easy | |
 | 266 | [Palindrome Permutation](https://leetcode.com/problems/palindrome-permutation) | Easy | |

src/BinaryTreePaths.java

@@ -0,0 +1,47 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class BinaryTreePaths {
+    public static void main(String[] args) {
+        String[] array = {"hello", "1", "2"};
+        List<CharSequence> list = new ArrayList<>();
+        list.add("1");
+        list.add("2");
+        list.add("3");
+        System.out.println(String.join("->", list));
+    }
+
+    private static class TreeNode {
+        int val;
+        TreeNode left;
+        TreeNode right;
+    }
+
+    public static List<String> binaryTreePaths(TreeNode root) {
+        List<String> result = new ArrayList<>();
+        binaryTreePaths(root, new ArrayList<CharSequence>(), result);
+        return result;
+    }
+
+    private static void binaryTreePaths(TreeNode root, List<CharSequence> path, List<String> paths) {
+        if (root == null) {
+            return;
+        }
+
+        path.add(root.val + "");
+
+        if (isLeafNode(root)) {
+            paths.add(String.join("->", path));
+            path.remove(path.size() - 1);
+            return;
+        }
+
+        binaryTreePaths(root.left, path, paths);
+        binaryTreePaths(root.right, path, paths);
+        path.remove(path.size() - 1);
+    }
+
+    private static boolean isLeafNode(TreeNode root) {
+        return root.left == null && root.right == null;
+    }
+}