[Leetcode] Sum Root to Leaf Numbers (Java)

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.

For example,

    1   / \  2   3

The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

计算所有路径和，DFS

public class Solution {    public int sumNumbers(TreeNode root) {        if(root==null)return 0;int ret=0;ArrayList<Integer> tmp = new ArrayList<Integer>();dfs(tmp,root,"");for(int i:tmp){ret+=i;}return ret;}private void dfs(ArrayList<Integer> tmp, TreeNode root,String string) {    string+=root.val;if(root.left==null&&root.right==null){tmp.add(Integer.parseInt(string));return;}if(root.left!=null)dfs(tmp, root.left, string);if(root.right!=null)dfs(tmp, root.right, string);}}