230621 전화번호 목록

public boolean solution(String[] phone_book) {
	Set<String> set = new HashSet<>(Arrays.asList(phone_book));

	for (String phone : phone_book) {
		for (int i = 1; i < phone.length(); i++) {
			if (set.contains(phone.substring(0, i))) {
				return false;
			}
		}
	}
	return true;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/42577