My code is as follows

public int counter = 0;

public int countPaths(TreeNode root, int S) {
    if (root == null) return 0;
    dfs(root, S, new ArrayList<>());
    return counter;
}

public void dfs(TreeNode root, int S, List<Integer> currentSequence) {
    if (root == null) return;

    currentSequence.add(root.val);
    if (root.left == null && root.right == null) {
        // check if any ordered subset has S
        int pathSum = 0;
        ListIterator<Integer> pathIterator = currentSequence.listIterator(currentSequence.size());
        while (pathIterator.hasPrevious()) {
            pathSum += pathIterator.previous();
            // if the sum of any sub-path is equal to 'S' we increment our path count.
            if (pathSum == S) {
                counter++;
            }
        }
    } else {
        dfs(root.left, S, currentSequence);
        dfs(root.right, S, currentSequence);
    }

    currentSequence.remove(currentSequence.size() - 1);
}

It fails for following test case

[1,0,1,1,null,6,5]

2

It seems count expected is 2? But from the input, to me seems like the count should only be 1?

Can you provide explanation or is it a bug in the test case?