129. Sum Root to Leaf Numbers

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

    1   / \  2   3

The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */class Solution {   public int sumNumbers(TreeNode root) {         if (root == null)             return 0;         if (root.left == null && root.right == null)             return root.val;         if (root.left != null) {             root.left.val = root.val * 10 + root.left.val;         }         if (root.right != null) {             root.right.val = root.val * 10 + root.right.val;         }         return sumNumbers(root.left) + sumNumbers(root.right);     } }