Q:
给定一个二叉树,返回它的 前序 遍历。
示例:
输入: [1,null,2,3]
1
\
2
/
3
输出: [1,2,3]
链接:https://leetcode-cn.com/problems/binary-tree-preorder-traversal/description/
思路:递归 前序遍历二叉树
代码:
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def preorderTraversal(self, root):
"""
:type root: TreeNode
:rtype: List[int]
"""
if root == None:
return []
else:
res = []
self.pre_digui(root, res)
return res
def pre_digui(self,root,res):
if root == None:
return
res.append(root.val)
self.pre_digui(root.left,res)
self.pre_digui(root.right,res)