gistfile1.txt

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.
Question: https://leetcode.com/problems/sum-root-to-leaf-numbers/

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    
    List<String> aList = new LinkedList<String>();
    
    public int sumNumbers(TreeNode root) {

        traverse(root, "");
        int sum = 0;
        for (String s : aList) {
            sum += Integer.parseInt(s);
        }
        
        return sum;
    }
    
    public void traverse(TreeNode root, String n) {
        
        if (root == null) {
            return;
        }
        
        if (root != null) {
            n += root.val;
        }
        
        if (root != null && root.left == null && root.right == null) {
            if (n != "") {
                aList.add(n);
            }
            return;
        }
        
        traverse(root.left, n);
        traverse(root.right, n);
    }
    
}