Sum Root to Leaf Numbers

1. Title

Sum Root to Leaf Numbers

2.   Http address

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

3. The question

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.

4. My code(AC)

 1 public  static void  DFS(TreeNode root, String str)
 2     {
 3         if( root == null)
 4                 return;
 5         if( root.left == null && root.right == null)
 6         {
 7             sum += Integer.parseInt(str + root.val);
 8             return;
 9         }
10 
11         DFS(root.right, str + root.val);
12         DFS(root.left, str + root.val);
13 
14     }
15     //Accepted
16     public static int sumNumbers(TreeNode root) {
17 
18             DFS(root,"");
19         return sum;
20 
21     }

原文：http://www.cnblogs.com/ordili/p/4928330.html