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dece 2021-12-14 16:30:27 +01:00
parent 9a350e8eea
commit 6ac2daf309

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2021/day14.py Normal file
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from collections import defaultdict
from math import ceil
with open("input14.txt") as f:
lines = [line.rstrip() for line in f]
template = lines[0]
rules = {k: v for k, v in map(lambda s: s.split(" -> "), lines[2:])}
pairs = defaultdict(int)
for i in range(len(template) - 1):
pairs[template[i:i+2]] += 1
# N B B B C N C C N B B N B N B B C H B H H B C H B
# NB BB BB BC CN NC CC CN NB BB BN NB BN NB BB BC CH HB BH HH HB BC CH HB
# N=5, B=11, C=5, H=4, but in pairs N=9, B=21, C=10, H=8
# so if odd: n+1 / 2 elif even: n / 2, which is ceil(n / 2) for both
for step in range(40):
for pair, n in list(pairs.items()):
if pairs[pair] == 0:
continue
mid = rules[pair]
new_pair1, new_pair2 = pair[0] + mid, mid + pair[1]
pairs[pair] -= n
pairs[new_pair1] += n
pairs[new_pair2] += n
if step in (9, 39):
pcount = defaultdict(int)
for pair, n in pairs.items():
for p in pair:
pcount[p] += n
tcount = {p: ceil(n / 2) for p, n in pcount.items()}
most_common = max(tcount, key=lambda p: tcount[p])
least_common = min(tcount, key=lambda p: tcount[p])
print(tcount[most_common] - tcount[least_common])