protected void addSequenceToProjection(Sequence sequence)
{
// keeps record of encountered items in the sequence
// to adding sequence more than once
HashSet<Item> seen = new HashSet<Item>(Item.EqComp);
for (int i = 0; i < sequence.NumTransactions; i++)
{
for(int k = 0; k < sequence[i].NumItems; k++)
{
Item item = sequence[i][k];
// already processed
if (seen.Contains(item))
continue;
else
seen.Add(item);
var pSeq = new PseudoSequence();
pSeq.Init(_nextPseudoSequenceIndex, i, k);
// point to the next item
// in the sequence
pSeq.PointToNextItem(sequence);
// add pseudo sequence to the list of projections
// for the current item
List<PseudoSequence> itemProjection;
if (!_projections.TryGetValue(item, out itemProjection))
{
itemProjection = new List<PseudoSequence>();
_projections.Add(item, itemProjection);
}
if (pSeq.IsValid)
itemProjection.Add(pSeq);
}
}
_nextPseudoSequenceIndex++;
}
public bool IsPrefixOf(Dictionary <Item, int> fDict, Sequence seq, PseudoSequence pSeq, out PseudoSequence suffix)
{
suffix = new PseudoSequence();
if (seq.IsEmpty)
{
return(false);
}
if (seq.NumTransactions - pSeq.TransactionIndex < 0)
{
return(false);
}
// current transaction index in prefix
var prefixTransactionIndex = 0;
// current item index in current prefix transaction
var prefixItemIndex = 0;
// current transaction index in suffix
var suffixTransactionIndex = pSeq.TransactionIndex;
// current item index in current suffix transaction
var suffixItemIndex = pSeq.ItemIndex;
// whether or not only last item needs to be matched to form a prefix
// e.g. prefix=<(abc)> suffix=<(_c)> only item c needs to be checked
// to validate new prefix
if (pSeq.ItemIndex != 0 || this.LastTransaction.NumItems == 1)
{
// only check last item since prefix already established
// from previous rounds
prefixTransactionIndex = this.NumTransactions - 1;
prefixItemIndex = this[prefixTransactionIndex].NumItems - 1;
if (pSeq.ItemIndex != 0 && this.LastTransaction.NumItems == 1)
{
suffixTransactionIndex++;
suffixItemIndex = 0;
}
}
for (int i = suffixTransactionIndex; i < seq.NumTransactions; i++)
{
int k = (i == suffixTransactionIndex) ? suffixItemIndex : 0;
for (; k < seq[i].NumItems; k++)
{
// if the current prefix item does not equal suffix item at [i, k]
if (!this[prefixTransactionIndex][prefixItemIndex].Equals(seq[i][k]))
{
// to form a prefix, all items in the last transaction of the prefix
// must be alphabetically AFTER all previous items in the transaction.
// The sorting step takes care of that, however, need to check for cases
// where two items have the same support making their ordering arbitrary
int support;
if (pSeq.ItemIndex == 0 || (fDict.TryGetValue(seq[i][k], out support) && support == fDict[this[prefixTransactionIndex][prefixItemIndex]]))
{
// items have same support, continue
continue;
}
// prefix not found in this transaction
break;
}
// items matched, continue to next item in prefix (if any)
prefixItemIndex++;
// no more items in current prefix transaction
// continue to next transaction (if any)
if (prefixItemIndex >= this[prefixTransactionIndex].NumItems)
{
// move to next transaction in prefix
prefixTransactionIndex++;
prefixItemIndex = 0;
// no more transactions, DONE!
if (prefixTransactionIndex >= this.NumTransactions)
{
// add the suffix pseudo sequence
suffix.Init(pSeq.SequenceIndex, i, k);
suffix.PointToNextItem(seq);
return(suffix.IsValid);
}
}
}
// reset the prefix transaction in the case that
// the transaction contains more than 1 item
// making a full transaction match necessary
if (this[prefixTransactionIndex].NumItems != 1)
{
prefixTransactionIndex = 0;
prefixItemIndex = 0;
}
}
return(false);
}
