【刷题DAY13】144, 145, 94.md

144, 145, 94. 二叉树的前序遍历、后序遍历、中序遍历

题目链接：https://leetcode.cn/problems/binary-tree-preorder-traversal/
https://leetcode.cn/problems/binary-tree-postorder-traversal/
https://leetcode.cn/problems/binary-tree-inorder-traversal/

0x1 看到题目的第一想法

• 0x2 自己实现过程中遇到哪些困难

• python实现

0x3 今日学习的文章链接，或者视频链接

• https://programmercarl.com/%E4%BA%8C%E5%8F%89%E6%A0%91%E7%9A%84%E9%80%92%E5%BD%92%E9%81%8D%E5%8E%86.html

0x4 看完代码随想录之后的想法

# 前序遍历-递归-LC144_二叉树的前序遍历
class Solution:
    def preorderTraversal(self, root: TreeNode) -> List[int]:
        # 保存结果
        result = []
        
        def traversal(root: TreeNode):
            if root == None:
                return
            result.append(root.val) # 前序
            traversal(root.left)    # 左
            traversal(root.right)   # 右

        traversal(root)
        return result

# 中序遍历-递归-LC94_二叉树的中序遍历
class Solution:
    def inorderTraversal(self, root: TreeNode) -> List[int]:
        result = []

        def traversal(root: TreeNode):
            if root == None:
                return
            traversal(root.left)    # 左
            result.append(root.val) # 中序
            traversal(root.right)   # 右

        traversal(root)
        return result

# 后序遍历-递归-LC145_二叉树的后序遍历
class Solution:
    def postorderTraversal(self, root: TreeNode) -> List[int]:
        result = []

        def traversal(root: TreeNode):
            if root == None:
                return
            traversal(root.left)    # 左
            traversal(root.right)   # 右
            result.append(root.val) # 后序

        traversal(root)
        return result