LeetCode Convert Sorted List to Binary Search Tree

Description:

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

Solution:

每次dfs记录开通和结束的节点下标，从而计算出他的长度。根据长度进行构造，和前面几道题目一样，算出中心位置的下标，取出val作为子节点。再往下递归。

import java.util.*;public class Solution {public TreeNode sortedListToBST(ListNode head) {int len = 0;ListNode temp = head;while (temp != null) {len++;temp = temp.next;}return dfs(head, 0, len - 1);}TreeNode dfs(ListNode head, int start, int end) {if (start > end)return null;int mid = (start + end) / 2;ListNode temp = head;for (int i = start; i < mid; i++)temp = temp.next;TreeNode root = new TreeNode(temp.val);root.left = dfs(head, start, mid - 1);root.right = dfs(temp.next, mid + 1, end);return root;}}