Question:

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

For example, given the following binary tree:

 

1 /   \2     3 \  5

 

All root-to-leaf paths are:

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

 

 Analysis:

问题描述：给出一棵二叉树，给出所有根节点到叶子节点的路径。

思路一：递归

Answer：

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    List
     
       res = new ArrayList
      
       ();    public List
       
         binaryTreePaths(TreeNode root) {        if(root != null)            findPath(root, Integer.toString(root.val));        return res;    }        public void findPath(TreeNode root, String string) {        // TODO Auto-generated method stub        if(root.left == null && root.right == null)            res.add(string);        if(root.left != null)            findPath(root.left, string + "->" + Integer.toString(root.left.val));        if(root.right != null)            findPath(root.right, string + "->" + Integer.toString(root.right.val));    }}
       
      
     

思路二：深度优先遍历，用栈保存遍历过的节点。