LeetCode--094--二叉树的中序遍历(python)

递归

 # Definition for a binary tree node.
 # class TreeNode:
 #     def __init__(self, x):
 #         self.val = x
 #         self.left = None
 #         self.right = None

 class Solution:
     def inorderTraversal(self, root: TreeNode) -> List[int]:
         if not root:
             return []
         return self.inorderTraversal(root.left)+ [root.val]+ self.inorderTraversal(root.right)

非递归

 class Solution:
     def inorderTraversal(self, root: TreeNode) -> List[int]:
         stack=[]
         res=[]
         while root or stack:
             if root:
                 stack.append(root)
                 root=root.left
             else:
                 root = stack.pop()
                 res.append(root.val)
                 root=root.right
         return res