LeetCode -- Convert SortedList To BST

题目描述：


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


就是把链表转化为二叉查找树


思路：
使用分治策略
1.把链表节点遍历，存在nodes集合中
2.用[0, length/2)节点创建左子树，用(length/2,n]节点创建右子树，使用nodes[length/2]来创建当前节点。




实现代码：

/** * Definition for singly-linked list. * public class ListNode { *     public int val; *     public ListNode next; *     public ListNode(int x) { val = x; } * } *//** * Definition for a binary tree node. * public class TreeNode { *     public int val; *     public TreeNode left; *     public TreeNode right; *     public TreeNode(int x) { val = x; } * } */public class Solution {    public TreeNode SortedListToBST(ListNode head) {        if(head == null){return null;}var nodes = new List<int>();while(head != null){nodes.Add(head.val);head = head.next;}TreeNode root = null;BuildTree(nodes,ref root);return root;}private void BuildTree(IList<int> values,ref TreeNode n){if(values.Count == 0){return;}var mid = (int)(values.Count/2);var self = values[mid];n = new TreeNode(self);var leftVals=  values.Where(x=>x < self);var rightVals = values.Where(x=>x > self);if(leftVals.Any()){BuildTree(leftVals.ToList() ,ref n.left);}if(rightVals.Any()){BuildTree(rightVals.ToList(),ref n.right);}}}