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from functools import cmp_to_key
def is_update_correct(update: list[str], rules: list[tuple[str, str]]) -> bool:
for idx, page in enumerate(update):
for previous_page in (update[previous_idx] for previous_idx in range(idx)):
if (page, previous_page) in rules:
return False
return True
rules = []
updates = []
reading_updates = False
with open("input") as f:
for line in f.readlines():
if reading_updates:
updates.append(line.strip().split(","))
elif line == "\n":
reading_updates = True
else:
rules.append(tuple(line.strip().split("|")))
for idx in range(len(updates) - 1, -1, -1):
if is_update_correct(updates[idx], rules):
updates.pop(idx)
for update in updates:
update.sort(key=cmp_to_key(lambda item1, item2: -1 if (item1, item2) in rules else 1 if (item2, item1) in rules else 0))
result = 0
for update in updates:
result += int(update[len(update) // 2])
print(result)
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