83 lines
2.6 KiB
Python
83 lines
2.6 KiB
Python
import collections
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import math
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import re
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def main():
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with open("day14.txt", "rt") as input_file:
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lines = [line.rstrip() for line in input_file.readlines()]
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line_re = re.compile(r"(.+) => (.+)")
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raw_reactions = [line_re.match(line).groups() for line in lines]
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reactions = {}
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for inputs, outputs in raw_reactions:
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mult, result = outputs.split(" ")
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input_comps = [i.split(" ") for i in inputs.split(", ")]
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input_tuples = [(int(q), n) for q, n in input_comps]
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reactions[result] = int(mult), input_tuples
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# Part 1
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ore_per_full = get_required_ore(reactions, 1)
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print("Required ore for 1 FUEL:", ore_per_full)
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# Part 2
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# Input gives 397771 OPF.
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# 10^12 ores with 13312 OPF example gives 82892753 FUEL.
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# 10^12 ores with 180697 OPF example gives 5586022 FUEL.
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# 10^12 ores with 2210736 OPF example gives 460664 FUEL.
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# 10^12 / 82892753 / 13312 ~= 0.91
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# 10^12 / 5586022 / 180697 ~= 0.99
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# 10^12 / 460664 / 2210736 ~= 0.98
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# Let's say our reaction will have an efficiency of ~ 0.985.
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# 10^12 / x / 397771 = 0.985 -> x = 2552294
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# Now on to our search.
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fuel_q = 2552294
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cursor = 2**16
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last_result = 0
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min_target = 10**12 - ore_per_full
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max_target = 10**12
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was_below = False
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while True:
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last_result = get_required_ore(reactions, fuel_q)
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print(f"{fuel_q} FUEL requires {last_result} ORE.")
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if cursor == 1:
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break
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if last_result < min_target:
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if not was_below:
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cursor //= 2
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fuel_q += cursor
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was_below = True
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elif last_result > max_target:
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if was_below:
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cursor //= 2
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fuel_q -= cursor
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was_below = False
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else:
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break
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def get_required_ore(reactions, quantity):
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stored_map = collections.defaultdict(int)
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needs = [("FUEL", quantity)]
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ore_per_full = 0
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while needs:
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needed, needed_q = needs.pop(0)
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if needed == "ORE":
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ore_per_full += needed_q
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continue
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react_mult, subcomps = reactions[needed]
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if stored_map[needed]:
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needed_q -= stored_map[needed]
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stored_map[needed] = 0
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num_reacts = math.ceil(needed_q / react_mult)
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if num_reacts:
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new_needs = [(name_sc, num_sc * num_reacts) for num_sc, name_sc in subcomps]
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needs += new_needs
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produced = react_mult * num_reacts
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if produced - needed_q > 0:
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stored_map[needed] += produced - needed_q
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return ore_per_full
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if __name__ == "__main__":
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main()
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