aoc19_14.awk

{
	gsub(/,/, "")

	incr[$NF] = $(NF-1)

	for (i = 1; i < NF-2; i += 2) {
		reqs[$NF, ++nreqs[$NF]] = $(i+1)
		qtys[$NF, $(i+1)] = $i
	}
}

END {
	print ore("FUEL", 1)
	print fuel(1000000000000)
}

function ore(chem, qty, mul, sum, i, req) {
	if (chem == "ORE")
		return qty

	if (ex[chem] < qty) {
		mul = int((qty-ex[chem] + incr[chem]-1) / incr[chem])
		ex[chem] += mul*incr[chem]
	}

	ex[chem] -= qty
	
	for (i = 1; i <= nreqs[chem]; i++) {
		req = reqs[chem, i]
		sum += ore(req, mul*qtys[chem, req])
	}

	return sum
}

function fuel(cargo, i, min, max, step) {
	step = 65536
	for (i = 1; step >= 1 || step <= -1; i += step) {
		delete ex
		if (ore("FUEL", i) < cargo) {
			min = i
			if (step < 0)
				step = -step/2
		}
		else {
			max = i
			if (step > 0)
				step = -step/2
		}
	}

	return min
}