leetcode 129. 求根节点到叶节点数字之和(java)

学习题解 重拳出击 喵喵喵

class Solution {
    public int sumNumbers(TreeNode root) {
        return bt(root, 0);
    }
    public int bt(TreeNode root, int tag){
        if(root == null) return 0;
        int tmp = tag * 10 + root.val;
        if(root.left == null && root.right == null){
            return tmp;
        }
        return bt(root.left, tmp) + bt(root.right, tmp);
    }
}