object PartTwo(string input)
{
var edges = input.Lines()
.Select(l => new Edge <string>(l.Substring(0, 3), l.Substring(4, 3)));
var graph = new QuikGraph.BidirectionalGraph <string, Edge <string> >();
var outerToInner = new Dictionary <string, string>();
foreach (var edge in edges)
{
graph.AddVertex(edge.Source);
if (!graph.ContainsVertex(edge.Target))
{
graph.AddVertex(edge.Target);
}
graph.AddEdge(edge);
outerToInner[edge.Target] = edge.Source;
}
var youPath = new List <string>();
var current = "YOU";
do
{
youPath.Add(current);
current = outerToInner[current];
} while (current != "COM");
var sanPath = new List <string>();
current = "SAN";
do
{
sanPath.Add(current);
current = outerToInner[current];
} while (current != "COM");
// Find the last common instance between the two paths
var outermostCommon = string.Empty;
foreach (var c in youPath)
{
if (sanPath.Contains(c))
{
outermostCommon = c;
break;
}
}
return(youPath.IndexOf(outermostCommon) + sanPath.IndexOf(outermostCommon) - 2);
}
object PartOne(string input)
{
var edges = input.Lines()
.Select(l => new Edge <string>(l.Substring(0, 3), l.Substring(4, 3)));
var graph = new QuikGraph.BidirectionalGraph <string, Edge <string> >();
foreach (var edge in edges)
{
graph.AddVertex(edge.Source);
if (!graph.ContainsVertex(edge.Target))
{
graph.AddVertex(edge.Target);
}
graph.AddEdge(edge);
}
var distanceFromCom = new Dictionary <string, int>();
var orbits = new Queue <string>();
orbits.Enqueue("COM");
distanceFromCom["COM"] = 0;
int totalOrbits = 0;
while (orbits.Count > 0)
{
var orbit = orbits.Dequeue();
if (graph.TryGetOutEdges(orbit, out var fromThis))
{
var distanceToThis = distanceFromCom[orbit] + 1;
foreach (var outerOrbit in fromThis)
{
distanceFromCom[outerOrbit.Target] = distanceToThis;
orbits.Enqueue(outerOrbit.Target);
totalOrbits += distanceToThis;
}
}
}
return(totalOrbits);
}