问题描述：

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

基本思路：

可以用二分的思想进行递归求解。

代码：

public TreeNode subSortedToBST(Vector<Integer> vec, int begin ,int end)  //Java
    {
        if(begin == end)
        {
            TreeNode node = new TreeNode(vec.get(begin));
            return node;
        }
        
        int mid = (begin + end)/2;
        TreeNode node = new TreeNode(vec.get(mid));
        if(mid != begin)
        {
            TreeNode left = subSortedToBST(vec,begin,mid-1);
            node.left = left;
        }
        if(mid != end)
        {
            TreeNode right = subSortedToBST(vec,mid+1,end);
            node.right = right;
        }
        return node;
    }
    public TreeNode sortedListToBST(ListNode head) {
        if(head == null)
            return null;
        
        Vector<Integer> array = new Vector<Integer>() ;
        while(head != null)
        {
            array.add(head.val);
            head = head.next;
        }
        
        TreeNode result = subSortedToBST(array,0,array.size()-1);
        return result;
        
    }

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