/**
1. 深搜不断累加路径上的值, 当累加到叶子节点时, 合并结果
2. 搜索顺序: 不断累加路径上的值
3. 搜索状态: cur, prev_value | result
4. 剪枝: cur == null 跳出
*/

/**
 * 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) {
        int[] result = new int[1];
        dfs(root, 0, result);
        return result[0];
    }

    public void dfs(TreeNode cur, int prev, int[] result){
        if (cur == null) return;
        int value = prev * 10 + cur.val;
        if (cur.left == null && cur.right == null) result[0] += value;
        dfs(cur.left, value, result);
        dfs(cur.right, value, result);
    }
}