mirror of
https://github.com/peter-tanner/advent-of-code-2020.git
synced 2024-11-30 19:00:17 +08:00
46 lines
1.5 KiB
Python
46 lines
1.5 KiB
Python
from collections import Counter
|
|
import itertools
|
|
import math
|
|
|
|
lines = { int(x) for x in open('input').read().splitlines() }
|
|
lines.add(0)
|
|
|
|
def a(transformers):
|
|
v = 0
|
|
dv = [3] #Always a 3v transformer at the end
|
|
while v < max(transformers):
|
|
v_ = min(set(range(v+1,v+4)).intersection(transformers))
|
|
dv.append(v_ - v)
|
|
v = v_
|
|
# print(dv)
|
|
|
|
count = dict(Counter(dv))
|
|
return count[3]*count[1]
|
|
|
|
def b(c, v, transformers):
|
|
for v_ in set(range(v+1,v+4)).intersection(lines):
|
|
# print(v_)
|
|
if v_ == max(transformers):
|
|
c += 1
|
|
else:
|
|
c = b(c, v_, transformers)
|
|
return c
|
|
# print(b(0, 0, lines)) #This is a recursive solution. IT works but it'll take an eternity to go through the whole list of transformers.
|
|
#My solution: Split the set by 'gaps' (where there is only one path through to the next number), then multiply together
|
|
def b_optimized(transformers):
|
|
rel = { v: set(range(v+1,v+4)).intersection(transformers) for v in transformers }
|
|
rel.pop(max(transformers))
|
|
gaps = { list(rel[x])[0] if (len(rel[x]) == 1) else None for x in rel }.intersection(transformers)
|
|
gaps.add(list(rel)[0])
|
|
gaps = sorted(gaps)
|
|
idx = 0
|
|
C = 1
|
|
while idx+1 < len(gaps):
|
|
s = sorted(set(range(gaps[idx],gaps[idx+1]+1)).intersection(transformers))
|
|
if len(s) > 2:
|
|
C *= b(0, list(s)[0], s)
|
|
idx += 1
|
|
return C
|
|
|
|
print(a(lines))
|
|
print(b_optimized(lines)) |