Binary Tree Paths

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

Given the following binary tree:

   1
 /   
2     3
 
  5

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；

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public class Solution {
  
    List<String> res = new ArrayList<String>();
    public List<String> binaryTreePaths(TreeNode root) {
        // Write your code here
        if(root != null) findPaths(root,String.valueOf(root.val));
        return res;
    }
    public void findPaths(TreeNode n,String path){
        if(n.left==null && n.right==null)   res.add(path);
        if(n.right!=null)   findPaths(n.right,path+"->"+n.right.val);
        if(n.left!= null)   findPaths(n.left ,path+"->"+n.left.val);
    }
}