蓝桥杯定向刷题：DFS篇

1.二叉树的所有叶子节点

给定一个二叉树，返回所有从根节点到叶子节点的路径。 说明: 叶子节点是指没有子节点的节点。

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public List binaryTreePaths(TreeNode root) {
        if(root == null){
            ArrayList list = new ArrayList();
            return list;
        }else if(root.right == null && root.left == null){
            ArrayList list = new ArrayList();
            list.add(Integer.toString(root.val));
            return list;
        }else{
            ArrayList list = new ArrayList();
            String tempstr = Integer.toString(root.val).concat("->");
            if(root.left != null){
                ArrayList temp = (ArrayList)binaryTreePaths(root.left);
                for(int i = 0; i