protected Digraph cut(BitSet vertices)
	{
		if(vertices.length() > vertexCount) return null;
		Digraph rv = new Digraph(vertexCount);
		for(int i = vertices.nextSetBit(0);i >= 0;i = vertices.nextSetBit(i+1))
		{
			for(int j = vertices.nextSetBit(0);j >= 0;j = vertices.nextSetBit(i+1))
			{
				rv.adjacencyMatrix[i][j] = adjacencyMatrix[i][j];
				if(rv.adjacencyMatrix[i][j] == true) rv.inDegrees[j]++;
			}
		}
		return rv;
	}