【LeetCode】109. Convert Sorted List to Binary Search Tree 解题报告(Python)

时间:2021-05-21 14:57:33

【LeetCode】109. Convert Sorted List to Binary Search Tree 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/convert-sorted-list-to-binary-search-tree/description/

题目描述:

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example:

Given the sorted linked list: [-10,-3,0,5,9],

One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:

      0
/ \
-3 9
/ /
-10 5

题目大意

把一个单链表转成二叉平衡树。二叉平衡树是左右子树的高度差最多为1.

解题方法

这个题目和108. Convert Sorted Array to Binary Search Tree基本一模一样啊!所以毫无疑问地,我把链表转成了数组,然后再用108题的做法就过了。

而且这个题神奇的地方在于,使用python2超时,但是使用Python3就通过了。以后还是尽量用python3比较好吧。。

哦对,python3要用地板除。

# Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = None # Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None class Solution:
def sortedListToBST(self, head):
"""
:type head: ListNode
:rtype: TreeNode
"""
nums = []
while head:
nums.append(head.val)
head = head.next
return self.helper(nums) def helper(self, nums):
if not nums: return None
_len = len(nums)
mid = _len // 2
root = TreeNode(nums[mid])
root.left = self.helper(nums[:mid])
root.right = self.helper(nums[mid+1:])
return root

日期

2018 年 6 月 23 日 ———— 美好的周末要从刷题开始