102 lines
3 KiB
Python
102 lines
3 KiB
Python
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def read_file():
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with open("input.txt","r") as f:
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groups = f.read().split('\n\n')
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rules = groups[0].split('\n')
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your_ticket = groups[1].split('\n')[1:]
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tickets = groups[2].split('\n')[1:]
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return rules, your_ticket, tickets
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def find_valid_set(rule):
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_, ranges = rule.split(': ')
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range1, range2 = ranges.split(' or ')
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a, b = map(int,range1.split('-'))
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c, d = map(int,range2.split('-'))
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set1 = set(range(a,b+1))
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set2 = set(range(c,d+1))
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return set1 | set2
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def find_valid_superset(rules):
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valid_superset = set()
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for rule in rules:
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valid_set = find_valid_set(rule)
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valid_superset = valid_superset | valid_set
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return valid_superset
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def part1(rules, tickets):
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"""Add up all values not valid for any range."""
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valid_set = find_valid_superset(rules)
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error_rate = 0
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for ticket in tickets:
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numbers = map(int,ticket.split(','))
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for number in numbers:
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if number not in valid_set:
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error_rate += number
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return error_rate
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def find_valid_tickets(tickets, rules):
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valid_tickets = []
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valid_set = find_valid_superset(rules)
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for ticket in tickets:
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numbers = map(int,ticket.split(','))
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if all([number in valid_set for number in numbers]):
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valid_tickets.append(ticket)
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return valid_tickets
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def parse_tickets(tickets):
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parsed_tickets = []
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for ticket in tickets:
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numbers = map(int,ticket.split(','))
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parsed_ticket = [int(number) for number in numbers]
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parsed_tickets.append(parsed_ticket)
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return parsed_tickets
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def part2(rules, your_ticket, tickets):
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"""Find product of 6 "departure" fields."""
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valid_tickets = find_valid_tickets(tickets, rules)
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valid_tickets += your_ticket
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parsed_tickets = parse_tickets(valid_tickets)
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your_ticket = parse_tickets(your_ticket)[0]
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ticket_length = len(parsed_tickets[0])
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ticket_count = len(parsed_tickets)
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# convert rules into valid sets
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valid_sets = []
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for i in range(ticket_length):
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valid_set = find_valid_set(rules[i])
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valid_sets.append(valid_set)
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# correlate rulesets with values
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possibilities = []
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for i in range(ticket_length):
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## get all values at position
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values = set()
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for ticket in parsed_tickets:
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values.add(ticket[i])
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## find which rulesets match
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possibility = []
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for j, valid_set in enumerate(valid_sets):
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if all([value in valid_set for value in values]):
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possibility.append(1)
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else:
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possibility.append(0)
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possibilities.append(possibility)
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# process of elimination to correlate ruleset to index
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mapping = {}
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for i in range(ticket_length):
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sums = list(map(sum, possibilities))
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i = sums.index(1) ## find row with only one 1
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row = possibilities[i]
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j = row.index(1) ## find 1 in that row
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mapping[j] = i
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for i in range(ticket_length):
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possibilities[i][j] = 0
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# this bit only works on actual input bc there's no reason to make it robust
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prod = 1
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for j in range(6):
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prod *= your_ticket[mapping[j]]
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return prod
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def main():
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rules, your_ticket, tickets = read_file()
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print(part1(rules, tickets), part2(rules, your_ticket, tickets))
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if __name__ == "__main__":
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main()
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