是论坛原题， 给个meal，meal有ingredients，一样ingredients的话就是一样的meal，求unique meals.答案写下面了, test cases全过了
public int uniqueMeal(List<Meal> meals){
Set<List<String>> set = new HashSet<List<String>>;
for (Meal m : meals) set.add(m.ingredients);
return set.size();
}