Sum Root to Leaf Numbers

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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);}}

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