94. 二叉树的中序遍历 （二叉树遍历整理）

二叉树遍历整理：

94. 二叉树的中序遍历 - 力扣（LeetCode）https://leetcode.cn/problems/binary-tree-inorder-traversal/solutions/324347/python3-er-cha-shu-suo-you-bian-li-mo-ban-ji-zhi-s/?envType=study-plan-v2&envId=top-100-liked

最易理解的代码：

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
        if not root:
            return []
        
        return self.inorderTraversal(root.left) + [root.val] + self.inorderTraversal(root.right)

栈：

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
        if not root:
            return []
        
        res = []
        stack = []
        cur = root
        while stack or cur:
            while cur:
                stack.append(cur)
                cur=cur.left
            cur = stack.pop()
            res.append(cur.val)
            cur=cur.right
        
        return res