// Run an amplifier series in feedback mode for all possible phase settings, get the best result.
public string PartTwo(string[] lines)
{
var source = new CPU(lines[0]);
const int permutations = 120;
return(Enumerable.Range(0, permutations).Max(seed => new AmplifierSeries(source, seed, true).RunAll()).ToString());
}
// Takes a "model" amplifier, which is copied to create instances, a "seed" (a number between 0 inclusive and
// 120 exclusive) which describes the phase settings, and a switch that, if true, links up the final amplifier
// back with the first one (as well as adjusting the final phase settings to use feedback mode).
public AmplifierSeries(CPU amplifierModel, int seed, bool withFeedback = false)
{
amplifiers = Enumerable.Repeat(0, 5).Select(_ => new Computer.V3(amplifierModel)).ToArray();
for (int i = 0; i < 4; i++)
{
amplifiers[i].OutputTo(amplifiers[i + 1]);
}
if (withFeedback)
{
amplifiers[4].OutputTo(amplifiers[0]);
}
var phaseSettings = PermutationFromIndex(seed);
for (int i = 0; i < 5; i++)
{
amplifiers[i].Input.Enqueue(phaseSettings[i] + (withFeedback ? 5 : 0));
}
amplifiers[0].Input.Enqueue(0);
}
