LeetCode(109) Convert Sorted List to Binary Search Tree

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

解题思路：

将节点转化为数组，然后递归求解

public class Solution {
public TreeNode sortedListToBST(ListNode head) {
if(head == null)
return null;
ArrayList nums = new ArrayList<Integer>();
while(head != null){
nums.add(head.val);
head = head.next;
}
return sortArrayToBST(nums,0,nums.size());
}
public TreeNode sortArrayToBST(List nums,int start,int end){
if(end < start)
return null;
int mid = (start+end)/2;
TreeNode root = new TreeNode((int)nums.get(mid));
root.left = sortArrayToBST(nums,start,mid-1);
root.right = sortArrayToBST(nums,mid+1,end);
return root;
}
}