题解 | #二叉树的前序遍历#

using System;
using System.Collections.Generic;

/*
public class TreeNode
{
	public int val;
	public TreeNode left;
	public TreeNode right;

	public TreeNode (int x)
	{
		val = x;
	}
}
*/

class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型一维数组
     */
    public List<int> preorderTraversal (TreeNode root) {
        // write code here
        List<int> list = new List<int>();
        Preorder(list,root);
        return list;
    }
    public void Preorder(List<int> list,TreeNode root)
    {
         
        if(root!=null)
        {
            list.Add(root.val);
            Preorder(list, root.left);
            Preorder(list, root.right);
        }
    }
}