public long GetOreRequirementFor(ReactionItem ri)
{
var pool = ReactionPool.InitWith(ri);
var reactionItem = ReduceToOre(pool);
return(reactionItem.Quantity);
}
public static ReactionPool InitWith(ReactionItem ri)
{
var pool = new ReactionPool();
pool[ri.Chemical] = ri;
return(pool);
}
private ReactionItem ReduceToOre(ReactionPool pool)
{
while (true)
{
var first = pool.FirstNonZeroNonOre();
if (first == null)
{
return(pool[Chemical.ORE]);
}
var chem = first.Value.Chemical;
var req = first.Value.Quantity;
var reaction = _reactions[chem];
var pos = reaction.Output.Quantity;
var act = DivU(req, pos);
var ris = reaction.Input
.Select(ri => act * ri)
.Append(-act * reaction.Output);
pool.Update(ris);
long DivU(long a, long b) => a % b == 0 ? a / b : (a / b) + 1;
}
}
