public FPNode(string item, FPNode parent)
{
this.item = item;
this.frequency = 1;
this.node_link = null;
this.parent = parent;
this.children = new List <FPNode>();
}
public FPTree(List <List <string> > transactions, UInt64 minimum_support_threshold)
{
this.root = new FPNode(Item({ }), null);