When I use the following code snippet with a HashSet to store square_nums, the output is 5 for n=23. Normally, it should produce the same output as the code below, which outputs 4. What am I missing?

Set<Integer> squareNums = new HashSet<>();
for (int i = 1; i * i <= n; i++) {
    squareNums.add(i * i);
}

Instead of:

ArrayList<Integer> squareNums = new ArrayList<>();
for (int i = 1; i * i <= n; ++i) {
    squareNums.add(i * i);
}

The whole correct solution from the Editorial is as follows:

    public int numSquares(int n) {
        ArrayList<Integer> squareNums = new ArrayList<>();
        for (int i = 1; i * i < n; i++) {
            squareNums.add(i*i);
        }
        Set<Integer> q = new HashSet<>();
        q.add(n);
        int level = 0;
        while (!q.isEmpty()) {
            level += 1;
            Set<Integer> next_q = new HashSet<>();
            for (Integer remainder : q) {
                for (Integer sq : squareNums) {
                    if (remainder.equals(sq)) return level;
                    else if (remainder < sq) break;
                    next_q.add(remainder - sq);
                }
            }
            q = next_q;
        }
        return level;
    }