2019: d14: ex2: add solution

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Bruno BELANYI 2019-12-14 17:46:19 +01:00
parent 2b15ae7552
commit d3445b2ef1

106
2019/d14/ex2/ex2.py Executable file
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#!/usr/bin/env python
import sys
from dataclasses import dataclass
from math import ceil
from typing import Dict, List
@dataclass
class Ingredient:
name: str
quantity: int
@dataclass
class ReactionEquation:
quantity: int
inputs: List[Ingredient]
Reactions = Dict[str, ReactionEquation]
def solve_for(n: int, reactions: Reactions) -> int:
ore_needed = 0
wanted = [("FUEL", n)]
excess: Dict[str, int] = {}
def provide_ingredient(name: str, wanted_quantity: int) -> None:
nonlocal ore_needed
nonlocal excess
nonlocal wanted
if name == "ORE":
ore_needed += wanted_quantity # There's no recipy for this one
return
if name in excess:
# Take from excess
if excess[name] > wanted_quantity:
excess[name] -= wanted_quantity
return # Nothing left to do
wanted_quantity -= excess[name]
del excess[name] # Took everything
if wanted_quantity == 0: # In case we provided just enough by excess
return
equation = reactions[name]
reaction_num = ceil(wanted_quantity / equation.quantity)
for ingredient in equation.inputs:
needed_quantity = ingredient.quantity * reaction_num
provide_ingredient(ingredient.name, needed_quantity)
produced_quantity = equation.quantity * reaction_num
excess_quantity = produced_quantity - wanted_quantity
if excess_quantity > 0:
if name in excess:
excess[name] += excess_quantity
else:
excess[name] = excess_quantity
while len(wanted) != 0:
provide_ingredient(*(wanted.pop()))
return ore_needed
def main() -> None:
reactions: Reactions = {}
def parse_react(l: str) -> None:
def parse_ingredient(i: str) -> Ingredient:
quantity, name = i.strip().split(" ")
return Ingredient(name, int(quantity))
input_list, output_str = l.split("=>")
inputs = [i for i in map(parse_ingredient, input_list.split(", "))]
output = parse_ingredient(output_str)
reactions[output.name] = ReactionEquation(output.quantity, inputs)
for line in sys.stdin.readlines():
parse_react(line)
for_one = solve_for(1, reactions)
target = 1000000000000
# Educated guesses about minimum and maximum fuel needed to use 'target' ORE
min_fuel_needed = target // for_one
max_fuel_needed = 2 * min_fuel_needed
while min_fuel_needed < max_fuel_needed:
# We already know that minimum value is valid, offset it by one for the search
mid = ceil((min_fuel_needed + max_fuel_needed) / 2)
mid_res = solve_for(mid, reactions)
if mid_res > target:
# Exclude the maximum that was already searched
max_fuel_needed = mid - 1
else:
# Keep the valid minimum value
min_fuel_needed = mid
print(max_fuel_needed)
if __name__ == "__main__":
main()