240106 불량 사용자

private Set<Set<String>> result;

public int solution(String[] userId, String[] bannedId) {
	result = new HashSet<>();
	dfs(new HashSet<>(), 0, userId, bannedId);
	return result.size();
}

private void dfs(Set<String> currentSet, int index, String[] userIds, String[] bannedId) {
	if (index == bannedId.length) {
		result.add(new HashSet<>(currentSet));
		return;
	}

	for (String userId : userIds) {
		if (!currentSet.contains(userId) && isMatching(userId, bannedId[index])) {
			currentSet.add(userId);
			dfs(currentSet, index + 1, userIds, bannedId);
			currentSet.remove(userId);
		}
	}
}

private boolean isMatching(String userId, String bannedId) {
	if (userId.length() != bannedId.length()) {
		return false;
	}
	for (int i = 0; i < bannedId.length(); i++) {
		if (bannedId.charAt(i) == '*') {
			continue;
		}
		if (userId.charAt(i) != bannedId.charAt(i)) {
			return false;
		}
	}
	return true;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/64064