object PartTwo(string input)
{
var data = input.Lines()
.Match(@"^(.*) => (\d+) (.*)$");
var reactions = new Dictionary <string, Reaction>();
foreach (var m in data)
{
var count = m.Groups.Count;
var result = new ChemAmount(m.Groups[count - 1].Value, int.Parse(m.Groups[count - 2].Value));
var chemAmounts = Regex.Matches(m.Groups[1].Value, @"(\d+) (\w+)")
.Cast <Match>()
.Select(m2 => m2.Groups.Cast <Group>().Skip(1).ToArray())
.Select(g2 => new ChemAmount(g2[1].Value, int.Parse(g2[0].Value)));
var reaction = new Reaction(chemAmounts, result);
reactions.Add(reaction.Result.Chemical, reaction);
}
const long oneTrillion = 1_000_000_000_000L;
// First step up until we've passed the storage
long step = 2;
long fuelRequested = 1;
long oreNeeded;
do
{
oreNeeded = OreNeeded(reactions, fuelRequested);
if (oreNeeded < oneTrillion)
{
fuelRequested = fuelRequested * step;
}
}while(oreNeeded < oneTrillion);
// Then we need to step down until we hit the sweet spot.
var lower = fuelRequested / step;
var tooHigh = fuelRequested;
do
{
fuelRequested = (tooHigh + lower) / 2;
oreNeeded = OreNeeded(reactions, fuelRequested);
if (oreNeeded < oneTrillion)
{
lower = fuelRequested;
}
else if (oreNeeded > oneTrillion)
{
tooHigh = fuelRequested;
}
else
{
lower = fuelRequested;
tooHigh = fuelRequested + 1;
}
}while(tooHigh - lower > 1);
return(lower);
}
object PartOne(string input)
{
var data = input.Lines()
.Match(@"^(.*) => (\d+) (.*)$");
var reactions = new Dictionary <string, Reaction>();
foreach (var m in data)
{
var count = m.Groups.Count;
var result = new ChemAmount(m.Groups[count - 1].Value, int.Parse(m.Groups[count - 2].Value));
var chemAmounts = Regex.Matches(m.Groups[1].Value, @"(\d+) (\w+)")
.Cast <Match>()
.Select(m2 => m2.Groups.Cast <Group>().Skip(1).ToArray())
.Select(g2 => new ChemAmount(g2[1].Value, int.Parse(g2[0].Value)));
var reaction = new Reaction(chemAmounts, result);
reactions.Add(reaction.Result.Chemical, reaction);
}
// Iterate all the reactions needed to go from FUEL to only ORE.
var fuelRequested = 1;
var oreNeeded = 0;
var chemsNeeded = new Dictionary <string, int>();
chemsNeeded.Add("FUEL", fuelRequested);
var extraChemicalsWeHave = new Dictionary <string, int>();
while (chemsNeeded.Count > 0)
{
// Take any chemical except ore to process.
var chemical = chemsNeeded.Keys.First();
var amountNeeded = chemsNeeded[chemical];
// Look up what it take to process it.
var reaction = reactions[chemical];
// How many times do we have to run the reaction to get the needed amount?
var timesToRunProcess = (int)Math.Ceiling((double)amountNeeded / reaction.Result.Amount);
// Add all the inputs to the list of chemicals needed.
foreach (var ca in reaction.Inputs)
{
var inputsNeeded = ca.Amount * timesToRunProcess;
// Do we have any leftovers from previous reactions?
var leftOvers = extraChemicalsWeHave.ContainsKey(ca.Chemical) ? extraChemicalsWeHave[ca.Chemical] : 0;
if (leftOvers >= inputsNeeded)
{
// There is more then enough of the leftovers so we do not have to process any more.
extraChemicalsWeHave[ca.Chemical] = leftOvers - inputsNeeded;
continue;
}
// There isn't enough of the leftovers. Let's take what we can, and process the rest.
inputsNeeded -= leftOvers;
extraChemicalsWeHave[ca.Chemical] = 0;
if (ca.Chemical == "ORE")
{
oreNeeded += inputsNeeded;
}
else if (!chemsNeeded.ContainsKey(ca.Chemical))
{
chemsNeeded.Add(ca.Chemical, inputsNeeded);
}
else
{
chemsNeeded[ca.Chemical] = chemsNeeded[ca.Chemical] + inputsNeeded;
}
}
// All the chemicals that are needed to process this chemical have been added.
// Remove the need to process this chemical.
chemsNeeded.Remove(reaction.Result.Chemical);
// Did we produce any extra chemicals?
var extrasProduced = timesToRunProcess * reaction.Result.Amount - amountNeeded;
extraChemicalsWeHave[reaction.Result.Chemical] = extraChemicalsWeHave.ContainsKey(reaction.Result.Chemical) ? extrasProduced + extraChemicalsWeHave[reaction.Result.Chemical] : extrasProduced;
}
// Did we have any leftovers that we did not need to process?
// TODO! (Not needed for part 1 - or at least I got the right answer anyways.)
return(oreNeeded);
}
public Reaction(IEnumerable <ChemAmount> inputs, ChemAmount result)
{
this.Inputs = inputs.ToList();
this.Result = result;
}
