Sum Root to Leaf Numbers

ReturnSumOfPathBinaryTree.java

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