LeetCode 129. 求根节点到叶节点数字之和 java题解

https://leetcode.cn/problems/sum-root-to-leaf-numbers/description/

class Solution {
    int res=0;
    public int sumNumbers(TreeNode root) {
        dfs(root,0);
        return res;
    }
    public void dfs(TreeNode root,int sum){
        if(root==null) return;
        sum=sum*10+root.val;
        if(root.left==null&&root.right==null){
            //叶子结点，找到一条路径
            res+=sum;
            sum=(sum-root.val)/10;//回溯
            return;
        }
        dfs(root.left,sum);
        dfs(root.right,sum);
    }
}