exercism_puzzles/python/cater-waiter/HINTS.md

Hints

General

• Sets are mutable, unordered collections with no duplicate elements.
• Sets can contain any data type, as long as all elements are hashable.
• Sets are iterable.
• Sets are most often used to quickly dedupe other collections or for membership testing.
• Sets also support mathematical operations like union, intersection, difference, and symmetric difference

1. Clean up Dish Ingredients

• The set() constructor can take any iterable as an argument. concept: lists are iterable.
• Remember: concept: tuples can be formed using (<element_1>, <element_2>) or via the tuple() constructor.

2. Cocktails and Mocktails

• A set is disjoint from another set if the two sets share no elements.
• The set() constructor can take any iterable as an argument. concept: lists are iterable.
• In Python, concept: strings can be concatenated with the + sign.

3. Categorize Dishes

• Using concept: loops to iterate through the available meal categories might be useful here.
• If all the elements of <set_1> are contained within <set_2>, then <set_1> <= <set_2>.
• The method equivalent of <= is <set>.issubset(<iterable>)
• concept: tuples can contain any data type, including other tuples. Tuples can be formed using (<element_1>, <element_2>) or via the tuple() constructor.
• Elements within concept: tuples can be accessed from the left using a 0-based index number, or from the right using a -1-based index number.
• The set() constructor can take any iterable as an argument. concept: lists are iterable.
• concept: strings can be concatenated with the + sign.

4. Label Allergens and Restricted Foods

• A set intersection are the elements shared between <set_1> and <set_2>.
• The set method equivalent of & is <set>.intersection(<iterable>)
• Elements within concept: tuples can be accessed from the left using a 0-based index number, or from the right using a -1-based index number.
• The set() constructor can take any iterable as an argument. concept: lists are iterable.
• concept: tuples can be formed using (<element_1>, <element_2>) or via the tuple() constructor.

5. Compile a "Master List" of Ingredients

• A set union is where <set_1> and <set_2> are combined into a single set
• The set method equivalent of | is <set>.union(<iterable>)
• Using concept: loops to iterate through the various dishes might be useful here.

6. Pull out Appetizers for Passing on Trays

• A set difference is where the elements of <set_2> are removed from <set_1>, e.g. <set_1> - <set_2>.
• The set method equivalent of - is <set>.difference(<iterable>)
• The set() constructor can take any iterable as an argument. concept: lists are iterable.
• The concept: list constructor can take any iterable as an argument. Sets are iterable.

7. Find Ingredients Used in Only One Recipe

• A set symmetric difference is where elements appear in <set_1> or <set_2>, but not both sets.
• A set symmetric difference is the same as subtracting the set intersection from the set union, e.g. (<set_1> | <set_2>) - (<set_1> & <set_2>)
• A symmetric difference of more than two sets will include elements that are repeated more than two times across the input sets. To remove these cross-set repeated elements, the intersections between set pairs needs to be subtracted from the symmetric difference.
• Using concept: loops to iterate through the various dishes might be useful here.