Binary Tree Paths

Given a binary tree, return all root-to-leaf paths.

Given the following binary tree:

All root-to-leaf paths are:

[ "1->2->5", "1->3" ]

解题思路：这道题目应该就是单纯的二叉树遍历，从根节点出发，遍历左右子节点并记录遍历路径，递归调用至叶节点；

 1 /**
 2  * Definition of TreeNode:
 3  * public class TreeNode {
 4  *     public int val;
 5  *     public TreeNode left, right;
 6  *     public TreeNode(int val) {
 7  *         this.val = val;
 8  *         this.left = this.right = null;
 9  *     }
10  * }
11  */
12 public class Solution {
13   
14     List<String> res = new ArrayList<String>();
15     public List<String> binaryTreePaths(TreeNode root) {
16         // Write your code here
17         if(root != null) findPaths(root,String.valueOf(root.val));
18         return res;
19     }
20     public void findPaths(TreeNode n,String path){
21         if(n.left==null && n.right==null)   res.add(path);
22         if(n.right!=null)   findPaths(n.right,path+"->"+n.right.val);
23         if(n.left!= null)   findPaths(n.left ,path+"->"+n.left.val);
24     }
25 }