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#!/usr/bin/python
def find_combos(sizes, taken, avail, remaining):
result = set()
# For each container we haven't used yet
for i in avail:
# If its capacity is less than what we need, recurse to find
# containers for the remaining liquid, which might not succeed.
if sizes[i] < remaining:
_taken = taken | {i}
_avail = avail - {i}
_remaining = remaining - sizes[i]
for c in find_combos(sizes, _taken, _avail, _remaining):
result |= {frozenset([i]) | c}
# If its capacity is exactly what we need, we've found an option
elif sizes[i] == remaining:
result |= {frozenset([i])}
# If its capacity is too large, this isn't an option; continue
return result
def solve_partn(partn, combos):
if partn == 1:
options = combos
else: # partn == 2
lengths = map(len, combos)
min_len = min(lengths)
options = {c for c in combos if len(c) == min_len}
return len(options)
def main():
# Read container volumes from the input text file
with open("input.txt", "r") as f:
sizes = list(map(int, f.read().splitlines()))
# Extremely expensive (takes several minutes), so do it once up front
combos = find_combos(sizes, set(), set(range(len(sizes))), 150)
print("Part 1 solution:", solve_partn(1, combos)) # 1304 for me
print("Part 2 solution:", solve_partn(2, combos)) # 18 for me
if __name__ == "__main__":
main()
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