Check sets contain/match the set of a set in Dart - dart

Question

A sets receipt is a set of sets:
Set dish1 = {'a', 'b'};
Set dish2 = {'c', 'd'};
Set dish3 = {'a', 'b', 'c'};
Set dish4 = {'a', 'b', 'c', 'd'};
Set receipt = {dish1, dish2, dish3, dish4};
I would like to find the logic that can test whether a material belongs to a certain dish of above receipt.
Set material1 = {'a', 'b'}; // return dish1
Set material2 = {'a', 'b', 'c'}; // dish3
Set material3 = {'a', 'b', 'd'}; // null
Set material4 = {'b', 'c', 'a'}; // dish3
material3 {'a', 'b', 'd'} returns null not the dish1 because I'm looking for an exact element match but the order doesn't matter so material4 {'b', 'c', 'a'} can return dish3.
Thank you.

Answer 1

To be able to have dish1, dish2, etc. available for your result, they actually have to be in your program. You can do this with a Map.
void main() {
var receipt = {
'dish1': {'a', 'b'},
'dish2': {'c', 'd'},
'dish3': {'a', 'b', 'c'},
'dish4': {'a', 'b', 'c', 'd'},
};
var availableIngredients = {'b', 'c', 'a'};
var dishesWithAvailableIngredients = receipt
.entries
.where(
(entry) => entry.value.containsAll(availableIngredients)
)
.map((entry) => entry.key);
print(dishesWithAvailableIngredients);
}
Of course, it might be nice to have some more structured data model in place:
void main() {
var receipt = new Receipt([
new Dish(name: 'dish1', ingredients: {'a', 'b'}),
new Dish(name: 'dish2', ingredients: {'c', 'd'}),
new Dish(name: 'dish3', ingredients: {'a', 'b', 'c'}),
new Dish(name: 'dish4', ingredients: {'a', 'b', 'c', 'd'}),
]);
print(receipt.dishesWithIngredients({'b', 'c', 'a'}));
}
class Dish {
// Might also want to track quantity, but I'm leaving that out
String name;
Set<String> ingredients;
Dish({String name, Set<String> ingredients}) {
this.name = name;
this.ingredients = ingredients;
}
bool containsAll(Set<String> ingredients) {
return this.ingredients.containsAll(ingredients);
}
String toString() {
return "Dish(name: ${name}, ingredients: ${ingredients})";
}
}
class Receipt {
List<Dish> dishes;
Receipt(List<Dish> dishes) {
this.dishes = dishes;
}
Iterable<Dish> dishesWithIngredients(Set<String> ingredients) {
return dishes.where((d) => d.containsAll(ingredients));
}
String toString() {
return "Receipt(dishes: ${dishes})";
}
}

Answer 2

You need a way to compare sets for equality, in order to see whether one set is equal to another.
You can use package:collection's SetEquality for that.
That would make the code to look up an set in set of sets:
Set? findDish(Set<Set> receipt, Set dish) {
for (var receiptDish in receipt) {
if (const SetEquality().equals(receiptDish, dish)) {
return receiptDish;
}
}
return null;
}
That's not particularly efficient. Instead you could use a custom hash map to store the receipts, and allow direct lookup by a set:
const setEquality = SetEquality();
Set<Set> receipt = HashSet<Set>(
equals: setEquality.equals, hashCode: setEquality.hash)
..addAll([dish1, dish2, dish3, dish4]);
Then you can directly look up a set in the other set:
Set? material1 = receipt.lookup({'a', 'b'}); // return dish1
Set? material2 = receipt.lookup({'a', 'b', 'c'}); // dish3
Set? material3 = receipt.lookup({'a', 'b', 'd'}); // null
Set? material4 = receipt.lookup({'b', 'c', 'a'}); // dish3