LeetCode--094--二叉树的中序遍历(python)

递归

 1 # Definition for a binary tree node.
 2 # class TreeNode:
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.left = None
 6 #         self.right = None
 7 
 8 class Solution:
 9     def inorderTraversal(self, root: TreeNode) -> List[int]:
10         if not root:
11             return []
12         return self.inorderTraversal(root.left)+ [root.val]+ self.inorderTraversal(root.right)

非递归

 1 class Solution:
 2     def inorderTraversal(self, root: TreeNode) -> List[int]:
 3         stack=[]
 4         res=[]
 5         while root or stack:
 6             if root:
 7                 stack.append(root)
 8                 root=root.left
 9             else:
10                 root = stack.pop()
11                 res.append(root.val)
12                 root=root.right
13         return res