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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {

    public int sumNumbers(TreeNode root) {
        long[] temp = new long[2];
        dfs(root, temp);
        return (int)temp[0];
    }
    
    public void dfs(TreeNode root, long[] temp) {
        if(root == null) return;
        if(root.left == null && root.right == null) {
            temp[0] += temp[1] * 10 + root.val;
        }
        
        temp[1] = temp[1] * 10 + root.val;
        dfs(root.left, temp);
        dfs(root.right, temp);
        temp[1] = (temp[1] - root.val) / 10;
    }
}