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File size: 1,875 Bytes
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with open("input.txt") as f:
data = f.readlines()
def check_rule(pages: list[str], rule):
page2idx = {p: idx for idx, p in enumerate(pages)}
r0, r1 = rule
idx0 = page2idx.get(r0)
idx1 = page2idx.get(r1)
if idx0 is None or idx1 is None:
return True # "pass"
return idx0 < idx1
def check_rules(pages, rules):
for rule in rules:
passes = check_rule(pages, rule)
if not passes:
return False
return True
rules = []
page_numbers = []
for line in data:
line = line.strip("\n")
if "|" in line:
r1, r2 = [int(r) for r in line.split("|")]
rules.append((r1, r2))
elif len(line) > 0:
page_numbers.append([int(r) for r in line.split(",")])
total = 0
for pages in page_numbers:
passes = check_rules(pages, rules)
if passes:
mid_idx = len(pages) // 2
total += pages[mid_idx]
print(total)
## Part 2
def return_failing_rule(pages, rules):
for rule in rules:
passes = check_rule(pages, rule)
if not passes:
return rule
return None
def update_pages(pages, failed_rule):
"Swap the pages given the failed rule"
page2idx = {p: idx for idx, p in enumerate(pages)}
r0, r1 = failed_rule
idx0 = page2idx.get(r0)
idx1 = page2idx.get(r1)
new_pages = pages.copy()
new_pages[idx0] = r1
new_pages[idx1] = r0
return new_pages
def fix_pages(pages, rules):
failed_rule = return_failing_rule(pages, rules)
while failed_rule:
pages = update_pages(pages, failed_rule)
failed_rule = return_failing_rule(pages, rules)
return pages
total = 0
for pages in page_numbers:
passes = check_rules(pages, rules)
if not passes:
new_pages = fix_pages(pages, rules)
mid_idx = len(pages) // 2
total += new_pages[mid_idx]
print(total)
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