共计 1081 个字符，预计需要花费 3 分钟才能阅读完成。
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.Note: A leaf is a node with no children.Example:
Input: [1,2,3]
1
/ \
2 3
Output: 25
Explanation:
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Therefore, sum = 12 + 13 = 25.
Example 2:
Input: [4,9,0,5,1]
4
/ \
9 0
/ \
5 1
Output: 1026
Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.
难度：medium
题目：给定结点值只包含 0 - 9 的二叉树，每条从根到叶子的路径表示一个整数。找出所有这样的数并返回其和。注意：叶结点即没有左右子结点
/**
* 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) {
return sumNumbers(root, “”);
}
private int sumNumbers(TreeNode root, String s) {
if (null == root) {
return 0;
}
s += root.val;
if (null == root.left && null == root.right) {
return Integer.parseInt(s);
}
return sumNumbers(root.left, s) + sumNumbers(root.right, s);
}
}