94. Binary Tree Inorder Traversal--python

题目:

Given a binary tree, return the inorder traversal of its nodes' values.

Example:

Follow up: Recursive solution is trivial, could you do it iteratively?

解题：

二叉树的中序遍历，可以用递归的方式

（关于中序遍历可以参考我的另一篇博客，详细介绍了中序，前序，后序的意思：点击打开链接）

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

class Solution(object):
    def inorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        if root==None:
            return []
        return self.inorderTraversal(root.left)+[root.val]+self.inorderTraversal(root.right)

也可以用栈的方式：

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

class Solution(object):
    def inorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        cur = root
        stack = []
        result = []
        while stack or cur:
            if cur:
                stack.append(cur)
                cur = cur.left
            else:
                cur = stack.pop()
                result.append(cur.val)
                cur = cur.right
        return result