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106 lines
3.0 KiB
Python
106 lines
3.0 KiB
Python
# /usr/bin/env python3
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import re
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from collections import defaultdict
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"""
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identify invalid nearby tickets by considering only whether tickets contain values that are not valid for any field.
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"""
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def main():
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rules, my_ticket, other_tickets = open("input.txt").read().split("\n\n")
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rules = parse_fields(rules)
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my_ticket = my_ticket.splitlines()[1]
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other_tickets = other_tickets.splitlines()[1:]
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print("Ticket scanning error rate ", part1(other_tickets, rules))
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part2(my_ticket, other_tickets, rules)
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def parse_fields(fields):
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fields_dict = {}
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for field in fields.splitlines():
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k, v = field.split(": ")
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ranges = re.findall(r"(\d+)-(\d+)", v)
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fields_dict[k] = [range(int(r[0]), int(r[1]) + 1) for r in ranges]
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return fields_dict
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def part1(tickets, rules):
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scanning_error_rate = 0
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for ticket in tickets:
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scanning_error_rate += sum(validate_ticket(ticket, rules))
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return scanning_error_rate
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def validate_ticket(ticket, rules):
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invalid_fields = []
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for value in ticket.split(","):
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value = int(value)
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if not validate_field(value, *rules.values()):
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invalid_fields.append(value)
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return invalid_fields
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def validate_field(field, *rules):
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validations = (any(field in r for r in rule) for rule in rules)
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return any(validations)
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def part2(my_ticket, other_tickets, rules):
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# filter only valid tickets
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valid_tickets = [ticket for ticket in other_tickets if validate_ticket(ticket, rules) == []]
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valid_tickets.append(my_ticket) # my ticket is valid
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# possible field for each index of a ticket
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candidates = defaultdict(set)
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for index in range(len(rules)):
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def inner():
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for rule_name, constraints in rules.items():
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for ticket in valid_tickets:
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field_value = int(ticket.split(",")[index])
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if not validate_field(field_value, constraints):
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return
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candidates[index].add(rule_name)
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inner()
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sorted_candidates = sort_candidates(candidates)
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fields_indexes = {}
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try:
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while len(fields_indexes) != len(rules):
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index, found = sorted_candidates.popitem()
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found = next(iter(found))
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fields_indexes[index] = found
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sorted_candidates = remove_item(sorted_candidates, found)
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except:
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pass
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fields_indexes = {k: v for k,v in fields_indexes.items() if v.startswith('departure')}
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total = 1
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my_ticket = my_ticket.split(',')
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for index in fields_indexes:
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total *= int(my_ticket[index])
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a = 1
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def sort_candidates(c):
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return {x: c[x] for x in sorted(c, key=lambda k: len(c[k]), reverse=True)}
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def remove_item(candidates, item):
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ret = {}
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for key, value in candidates.items():
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try:
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value.remove(item)
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except ValueError:
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pass
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ret[key] = value
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#candidates = {k: set(v - item) for k,v in candidates.items()}
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return ret
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if __name__ == "__main__":
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main()
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