Day 7: Handy Haversacks

Functions:

parse_bagexpr(text)	Parse the expression representing a bag.
parse_rule(text)	Parse the rule from the text given as a single line.
parse_rules(lines)	Parse the rules from the given lines.
directly_contains(container, contained, rules)	Check whether the contained is contained in the container.
containers(kind, rules)	Compute the set of known containers.
count_containers(lines)	Parse the rules given as lines and count the allowed containers.
main()	Execute the main routine.

parse_bagexpr(text: str) → Tuple[int, str]

Parse the expression representing a bag.

Returns

number of units, kind

Requires

• re.fullmatch(r"d+ .* bags?", text)

parse_rule(text: str) → Tuple[str, Dict[str, int]]

Parse the rule from the text given as a single line.

Returns

kind, contents

Requires

• "n" not in text

parse_rules(lines: Lines) → Dict[str, Dict[str, int]]

Parse the rules from the given lines.

directly_contains(container: str, contained: str, rules: Dict[str, Dict[str, int]]) → bool

Check whether the contained is contained in the container.

containers(kind: str, rules: Dict[str, Dict[str, int]]) → Set[str]

Compute the set of known containers.

Ensures

• all(
      not directly_contains(non_container, container, rules)
      for non_container in (rules.keys() - result)
      for container in result
  )
  

  (Nothing else contains anything in the result)

• kind in result

  (given kind is in the result)

count_containers(lines: Lines) → int

Parse the rules given as lines and count the allowed containers.

main() → None

Execute the main routine.