题目：

题解：

class Solution {ListNode globalHead;public TreeNode sortedListToBST(ListNode head) {globalHead = head;int length = getLength(head);return buildTree(0, length - 1);}public int getLength(ListNode head) {int ret = 0;while (head != null) {++ret;head = head.next;}return ret;}public TreeNode buildTree(int left, int right) {if (left > right) {return null;}int mid = (left + right + 1) / 2;TreeNode root = new TreeNode();root.left = buildTree(left, mid - 1);root.val = globalHead.val;globalHead = globalHead.next;root.right = buildTree(mid + 1, right);return root;}
}