1 /** 2  * Definition for singly-linked list. 3  * public class ListNode { 4  *     int val; 5  *     ListNode next; 6  *     ListNode(int x) { val = x; next = null; } 7  * } 8  */ 9 /**10  * Definition for binary tree11  * public class TreeNode {12  *     int val;13  *     TreeNode left;14  *     TreeNode right;15  *     TreeNode(int x) { val = x; }16  * }17  */18 public class Solution {19     public TreeNode sortedListToBST(ListNode head) {20         ArrayList<ListNode> listNodes=new ArrayList<ListNode>();21         if (head==null) return null;22         ListNode node=head;23         while (node!=null) {24             listNodes.add(node);25             node=node.next;26         }27         int middle=(listNodes.size()-1)/2;28         TreeNode root =new TreeNode(listNodes.get(middle).val);29         if (middle>0){30             listNodes.get(middle-1).next=null;31             root.left=sortedListToBST(listNodes.get(0));32 33         }34         if (middle<listNodes.size()-1){35             root.right=sortedListToBST(listNodes.get(middle+1));36 37         }38         return root;39 40     }41 }