题解 | 二叉树的前序遍历

class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None
#
# 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
#
class Solution:
    def preorderTraversal(self , root: TreeNode) -> List[int]:
        result=[]
        def preorder(root):
            if root:
                result.append(root.val)
                preorder(root.left)
                preorder(root.right)
        preorder(root)
        return result

还是递归好写