Sum Root to Leaf Numbers

题目原型：

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

.

基本思路：

本题的意思就是把每条路径代表的值想加，关键就是求路径。

public List<Integer> list = new ArrayList<Integer>();
public int sumNumbers(TreeNode root)
{
if(root==null)
return 0;
int sum = 0;
search(root, "");
for(Integer in : list)
{
sum+=in;
}
return sum;
}

public void search(TreeNode root,String str)
{
if(root.left==null&&root.right==null)
{
str = str + root.val;
list.add(Integer.parseInt(str));
}
else
{
if(root.left!=null)
search(root.left, str+root.val);
if(root.right!=null)
search(root.right, str+root.val);
}
}