257.Binary Tree Paths

问题描述

将一棵二叉树所有的路径写出来
如：

输出结果如下：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */

// 中序遍历 DFS
class Solution {
    public List<String> list = new ArrayList<String>();
    public List<String> binaryTreePaths(TreeNode root) {  
        if( root == null ) return list;
        t(root,root.val+"");
        System.out.println("hh");
        return list;
    }
    public void t(TreeNode tn,String s){
        if( tn.left == null && tn.right == null ){
            list.add(s);
        }
        if(tn.left != null){
           t(tn.left,s+"->"+tn.left.val);
        }
            
        if(tn.right != null)
           t(tn.right,s+"->"+tn.right.val);
    }
}