class Solution {    ListNode lnode=null;    public TreeNode sortedListToBST(ListNode head) {        int size=0;        ListNode p=head;        while(p!=null)        {            p=p.next;            size++;        }        lnode=head;        return buildBST(size);    }    private TreeNode buildBST(int size){        if(size==0)            return null;        TreeNode tnode=new TreeNode(0);        tnode.left=buildBST(size/2);        tnode.val=lnode.val;        lnode=lnode.next;        tnode.right=buildBST(size-size/2-1);        return tnode;    }}