56 lines
1.5 KiB
Python
56 lines
1.5 KiB
Python
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import aocd
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import collections
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def parse_rules(orders):
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"""
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Return a dictionary mapping page numbers to lists of page numbers
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For any given key, each page of the value must come after it
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"""
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rules = collections.defaultdict(list)
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for order in orders:
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k,v = order.split('|')
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rules[k].append(v)
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return rules
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def update_is_incorrect(update, rules):
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for n, page in enumerate(update):
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for prev_n, prev_page in enumerate(update[:n]):
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if prev_page in rules[page]:
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return (n, prev_n)
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return False
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def fix_update(update, rules):
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def insert_before(l, a, b):
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"""
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Mutate l with the bth element moved to just before the ath
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"""
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l.insert(a, l.pop(b))
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while (indices := update_is_incorrect(update, rules)):
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insert_before(update, *indices)
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return int(update[len(update)//2])
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def solve(data):
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orders, updates = data.split('\n\n')
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updates = (u.split(',') for u in updates.split('\n'))
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rules = parse_rules(orders.split('\n'))
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incorrect = (u for u in updates if update_is_incorrect(u, rules))
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return sum(fix_update(u, rules) for u in incorrect)
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if __name__ == '__main__':
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print('Warning: This is horrifically slow but I do not feel like spending time on a sorting problem', file=__import__('sys').stderr)
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puz = aocd.models.Puzzle(year=2024, day=5)
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# data = puz.examples[0].input_data
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data = puz.input_data
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solution = solve(data)
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print(solution)
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aocd.submit(solution, year=2024, day=5, part='b')
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