Convert Sorted List to Binary Search Tree

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; next = null; }
 * }
 */
/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode sortedListToBST(ListNode head) {
        // Start typing your Java solution below
        // DO NOT write main() function
        //ArrayList<Integer> a = new ArrayList<Integer>();
        if(head==null)return null;
        int count = 0;
        int i = 0;
        ListNode t = head;
        while(t!=null){
            count++;t = t.next;
        }
        t = head;
        int[] num = new int[count];
        while(t!=null){
            num[i++] = t.val;
            t = t.next;
        }
        return mid(num,0,count-1);
        
    }
    private TreeNode mid(int[] num,int begin,int end){
        if(begin==end){
            return new TreeNode(num[begin]);    
        }
        else{
            int cur = begin+(end+1-begin)/2;
            TreeNode t = new TreeNode(num[cur]);
            t.left = mid(num,begin,cur-1);
            if(cur!=end)t.right = mid(num,cur+1,end);
            return t;
        }
    }
    
}

這個題有點偷懶了