private static Dictionary <string, long> GrowPolymerCounts(PolymerInstructions polymerInstruction, Dictionary <string, long> pairCount)
{
Dictionary <string, long> newCounts = new Dictionary <string, long>();
foreach (var pair in pairCount.Keys)
{
var monomer = polymerInstruction.InsertionRules[pair];
var newPair1 = string.Concat(pair[0], monomer);
var newPair2 = string.Concat(monomer, pair[1]);
if (newCounts.ContainsKey(newPair1))
{
newCounts[newPair1] += pairCount[pair];
}
else
{
newCounts.Add(newPair1, pairCount[pair]);
}
if (newCounts.ContainsKey(newPair2))
{
newCounts[newPair2] += pairCount[pair];
}
else
{
newCounts.Add(newPair2, pairCount[pair]);
}
}
return(newCounts);
}
private static long RunCount(PolymerInstructions polymerInstruction, int steps)
{
var polymer = polymerInstruction.Template;
var pairCount = new Dictionary <string, long>();
for (int i = 0; i < polymer.Length - 1; i++)
{
var p1 = polymer[i];
var p3 = polymer[i + 1];
string pair = string.Concat(p1, p3);
if (pairCount.ContainsKey(pair))
{
pairCount[pair] += 1;
}
else
{
pairCount.Add(pair, 1);
}
}
for (int step = 0; step < steps; step++)
{
pairCount = GrowPolymerCounts(polymerInstruction, pairCount);
}
var monomerCounts = pairCount.SelectMany(p => p.Key.ToArray().Select(c => new { Key = c, Count = p.Value }))
.GroupBy(a => a.Key).Select(grp => new { Key = grp.Key, Count = grp.Sum(g => g.Count) }).ToDictionary(k => k.Key, c => c.Count);
monomerCounts[polymer.First()] += 1;
monomerCounts[polymer.Last()] += 1;
//All characters are counted twice now!
var difference = (monomerCounts.Max(m => m.Value) - monomerCounts.Min(m => m.Value)) / 2;
return(difference);
}
private static string GrowPolymer(PolymerInstructions polymerInstruction, string polymer)
{
var sb = new StringBuilder();
sb.Append(polymer[0]);
for (int i = 0; i < polymer.Length - 1; i++)
{
var p1 = polymer[i];
var p3 = polymer[i + 1];
string pair = string.Concat(p1, p3);
var p2 = polymerInstruction.InsertionRules[pair];
sb.Append(p2);
sb.Append(p3);
}
polymer = sb.ToString();
return(polymer);
}
private static long RunPolymerization(PolymerInstructions polymerInstruction, int steps)
{
var polymer = polymerInstruction.Template;
for (int step = 0; step < steps; step++)
{
polymer = GrowPolymer(polymerInstruction, polymer);
}
var monomerCounts = polymer.GroupBy(p => p).Select(p => new
{
Monomer = p.First(),
Count = p.LongCount()
});
var difference = monomerCounts.Max(m => m.Count) - monomerCounts.Min(m => m.Count);
return(difference);
}
public PolymerInstructions ParseFile(string filePath)
{
var instructions = new PolymerInstructions();
var mode = 0;
foreach (var line in ReadData(filePath))
{
if (string.IsNullOrWhiteSpace(line))
{
mode++;
continue;
}
if (mode == 0)
{
instructions.Template = line;
}
else if (mode == 1)
{
instructions.InsertionRules.Add(line.Substring(0, 2), line[6]);
}
}
return(instructions);
}
