private static CycleRecord GroupStartingFrom(int start, List <int> BFFs)
{
var visited = new bool[BFFs.Count];
var previous = -1;
var current = start;
visited[current] = true;
while (!visited[BFFs[current]])
{
previous = current;
current = BFFs[current];
visited[current] = true;
}
var openGroup = BFFs[current] == previous;
if (BFFs[current] != start && !openGroup)
{
return(new CycleRecord {
isSuccess = false
});
}
var record = new CycleRecord()
{
visited = visited,
isOpen = openGroup,
isSuccess = true,
};
return(record);
}
private static bool IsCompatible(CycleRecord record)
{
foreach (var current in currentSubset)
{
if (!current.IsCompatibleWith(record))
{
return(false);
}
}
return(true);
}
public bool IsCompatibleWith(CycleRecord other)
{
if (visited.Length != other.visited.Length)
{
return(false);
}
for (int i = 0; i < visited.Length; i++)
{
if (other.visited[i] && visited[i])
{
return(false);
}
}
return(true);
}
private static int SizeOfLargestCircle(List <int> BFFs)
{
var cycleRecords = new CycleRecord[BFFs.Count];
for (int i = 0; i < BFFs.Count; i++)
{
cycleRecords[i] = GroupStartingFrom(i, BFFs);
}
var largestClosed = cycleRecords.Where(r => r.isSuccess).Max(r => r.GetSize());
currentSubset = new List <CycleRecord>();
var largestOpenCombination = GetLargestCompatibleSubSet(cycleRecords.Where(r => r.isSuccess && r.isOpen).ToList());
return(largestClosed > largestOpenCombination ? largestClosed : largestOpenCombination);
}
