AoC 2019 Day 14 Part 2

from gurobipy import *
import re

ruleRe = re.compile("(\d+) (\w+)")

with open("input14.txt") as f:
    model = Model("fuel")

    chemicals = {}
    ruleVars = {}
    chemicals2rules = {}
    leftovers = {}

    rules = []

    model.modelSense = GRB.MAXIMIZE

    for i,line in enumerate(f):
        rule = line.split("=>")

        lh = [ ruleRe.match(r.strip()).groups() for r in rule[0].strip().split(",") ]
        rh = ruleRe.match(rule[1].strip()).groups()

        # add vars
        for quant,chem in lh:
            if not chem in chemicals:
                chemicals2rules[chem] = { "lh": [], "rh": [] }
                chemicals[chem] = model.addVar(vtype=GRB.INTEGER, lb=0, obj=0)

            chemicals2rules[chem]["lh"].append((i, int(quant)))

        if not rh[1] in chemicals:
            chemicals2rules[rh[1]] = { "lh": [], "rh": [] }
            chemicals[rh[1]] = model.addVar(vtype=GRB.INTEGER, lb=0, obj=0)

        chemicals2rules[rh[1]]["rh"].append((i, int(rh[0])))

        ruleVars[i] = model.addVar(vtype=GRB.INTEGER, lb=0, obj=0)

        rules.append((lh, rh))

    chemicals["FUEL"].obj = 1
    # chemicals["ORE"].obj = 0

    for chem in chemicals:
        leftovers[chem] = model.addVar(vtype=GRB.INTEGER, lb=0, obj=-1)

    # add rules
    for chem in chemicals:
        if len(chemicals2rules[chem]["rh"]) > 0:
            # the quantity of chemicals is equal to the produced amount
            model.addConstr(quicksum(quant * ruleVars[rule] for rule,quant in chemicals2rules[chem]["rh"]) == chemicals[chem])

        if len(chemicals2rules[chem]["lh"]) > 0:
            # the quantity of chemicals has to be equal or larger than the needed amount for all rules
            model.addConstr(quicksum(quant * ruleVars[rule] for rule,quant in chemicals2rules[chem]["lh"]) <= chemicals[chem])

            # the leftovers are >produced amount< - >required amount<
            model.addConstr(chemicals[chem] - quicksum(quant * ruleVars[rule] for rule,quant in chemicals2rules[chem]["lh"]) == leftovers[chem])

    model.addConstr(chemicals["ORE"] == 1000000000000)

    model.optimize()

    # print solution
    for chem in chemicals:
        print("Require {} of type {}".format(chemicals[chem].x, chem))

    for r in ruleVars:
        print("Rule {} was applied {} times".format(r, ruleVars[r].x))

    print(chemicals["FUEL"].x)