leetcode刷题250天(23)——二叉树的前中后序遍历(递归版)

class Solution(object):
    def preorderTraversal(self, root):
        # 前序遍历
        res = []
        def dfs(node):
            if node is None:
                return

            res.append(node.val)
            dfs(node.left)
            dfs(node.right)

        dfs(root)
        return res
        
class Solution(object):
    def inorderTraversal(self, root):
        # 中序遍历
        res = []
        def Middle_order(node):
            if node is None:
                return

            Middle_order(node.left)
            res.append(node.val)
            Middle_order(node.right)

        Middle_order(root)
        return res
        
class Solution:
    def postorderTraversal(self, root):
    # 后序遍历
        list_ = []
        def postorder(root):
            if root is None:
                return

            postorder(root.left)
            postorder(root.right)
            list_.append(root.val)
            
        postorder(root)
        return list_