【LeetCode】105. Construct Binary Tree from Preorder and Inorder Traversal 解题报告(Python)
标签(空格分隔): LeetCode
作者: 负雪明烛
id: fuxuemingzhu
个人博客: http://fuxuemingzhu.me/
题目地址:https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/description/
题目描述:
Given preorder and inorder traversal of a tree, construct the binary tree.
Note:
You may assume that duplicates do not exist in the tree.
For example, given
preorder = [3,9,20,15,7]
inorder = [9,3,15,20,7]
Return the following binary tree:
3
/ \
9 20
/ \
15 7
题目大意
使用先序遍历和中序遍历重构二叉树
解题方法
这个题基本功了吧。简单分析一下,先序遍历的开头第一个元素是根元素,找到其在中序遍历中的位置,分割出左右子树。再根据左右子树的长度在先序遍历中划分。
# 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 buildTree(self, preorder, inorder):
"""
:type preorder: List[int]
:type inorder: List[int]
:rtype: TreeNode
"""
if not preorder or not inorder:
return None
root = TreeNode(preorder[0])
index = inorder.index(preorder[0])
root.left = self.buildTree(preorder[1:index+1], inorder[:index])
root.right = self.buildTree(preorder[index+1:], inorder[index+1:])
return root
日期
2018 年 6 月 22 日 ———— 这周的糟心事终于完了