Sum Root to Leaf Numbers

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题目描述：

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 number123.

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.

题目比较简单，就是找到叶子节点，记录中间经过的值，到根节点的时候加入到sum中。

代码如下：

public class Solution {    int sum=0;public int sumNumbers(TreeNode root) {if(root==null)return 0;subSumNumbers(root, 0);return sum;    }public void subSumNumbers(TreeNode root,int num){if(root.left==null&&root.right==null)sum+=num*10+root.val;if(root.left!=null)subSumNumbers(root.left, num*10+root.val);if(root.right!=null)subSumNumbers(root.right, num*10+root.val);}}

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