internal Set <Set <Set <T> > > GetAllPartitions()
{
var firstPartition = new Set <Set <T> >()
{
this
};
var result = new Set <Set <Set <T> > >()
{
firstPartition
};
MakeAllPartititionsOfCurrentSet(firstPartition);
return(result);
void MakeAllPartititionsOfCurrentSet(Set <Set <T> > currentSet)
{
foreach (var set in currentSet)
{
if (set.Count > 1)
{
var workSet = new Set <T>(set);
var rest = new Set <Set <T> >(currentSet);
rest.Remove(set);
if (workSet.Count < 2)
{
return;
}
var bitMask = new BitMask(workSet.Count);
while (bitMask.SetToNextCombination())
{
MakeSmallPartition(workSet, bitMask, out Set <T> leftSet, out Set <T> rightSet);
if ((leftSet.Count == 0) || (rightSet.Count == 0))
{
continue;
}
var smallSet = new Set <Set <T> >(rest);
smallSet.Add(leftSet);
smallSet.Add(rightSet);
if (result.Contains(smallSet))
{
continue;
}
result.Add(smallSet);
MakeAllPartititionsOfCurrentSet(smallSet);
}
}
}
static void MakeSmallPartition(Set <T> workSet, BitMask bitMask, out Set <T> leftSet, out Set <T> rightSet)
{
var setEnum = workSet.GetEnumerator();
var bitMaskEnum = bitMask.GetEnumerator();
rightSet = new Set <T>();
leftSet = new Set <T>();
while (bitMaskEnum.MoveNext() && setEnum.MoveNext())
{
if (bitMaskEnum.Current)
{
leftSet.Add(setEnum.Current);
}
else
{
rightSet.Add(setEnum.Current);
}
}
}