[2019/14] p1 solved

2019/14/example

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+10 ORE => 10 A
+1 ORE => 1 B
+7 A, 1 B => 1 C
+7 A, 1 C => 1 D
+7 A, 1 D => 1 E
+7 A, 1 E => 1 FUEL

2019/14/script.py

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+from GhostyUtils import aoc
+import math
+from collections import defaultdict, deque
+
+
+def ore_for_n_fuel(fuel: int, reactions: dict) -> int:
+    required = deque()
+    required.append(('FUEL', fuel))
+    leftovers = defaultdict(int)
+    ore = 0
+
+    # while we still have chemicals to make...
+    while required:
+        # take a chemical from the queue
+        product, amount = required.popleft()
+
+        # use materials from our leftover pile, if we have enough to cover the whole cost
+        if amount <= leftovers[product]:
+            leftovers[product] -= amount
+            continue
+
+        # use up any leftovers we might have
+        to_create = amount - leftovers[product]
+        del leftovers[product]
+
+        # calculate how many reactions we need to do
+        creates = reactions[product]['creates']
+        num_reactions = math.ceil(to_create / creates)
+
+        # add leftovers to our pile
+        leftover = (creates * num_reactions) - to_create
+        leftovers[product] += leftover
+
+        # add all the reactants to make this product to the queue
+        for reactant, amount in reactions[product]['reactants'].items():
+            # if our reactant is ore, add to the ore count instead
+            if reactant == 'ORE':
+                ore += amount * num_reactions
+            else:
+                required.append((reactant, amount * num_reactions))
+
+    return ore
+
+
+def main():
+    reactions_txt = aoc.read_lines()
+
+    reactions = {}
+    for reaction in reactions_txt:
+        input, output = reaction.split(' => ')
+        inputs = input.split(', ')
+        amount, name = output.split()
+        chemicals = {name: int(amount) for amount, name in map(str.split, inputs)}
+        reactions[name] = {'creates': int(amount), 'reactants': chemicals}
+
+    ore = ore_for_n_fuel(1, reactions)
+    print('p1:', ore)
+
+
+if __name__ == "__main__":
+    main()