Convert Sorted List to Binary Search Tree LeetCode solution in Java

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class Solution {
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  public TreeNode sortedListToBST(ListNode head) {
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    ListNode tmp = head;
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    ArrayList<Integer> treelist = new ArrayList<>();
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    while (tmp != null) {
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      treelist.add(tmp.val);
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      tmp = tmp.next;
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    }
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    return createTree(treelist, 0, treelist.size() - 1);
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  }
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  public TreeNode createTree(ArrayList<Integer> treelist, int start, int end) {
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    if (start > end) return null;
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    int mid = start + (end - start) / 2;
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    TreeNode node = new TreeNode(treelist.get(mid)); // getNode(treelist.get(mid));
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    node.left = createTree(treelist, start, mid - 1);
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    node.right = createTree(treelist, mid + 1, end);
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    return node;
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  }
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}