int cmp = source.compareTo(other.source); if (cmp != 0) return cmp; cmp = dest.compareTo(other.dest);
int cmp = super.compareTo(other);
	public int compareTo(Edge other) {		// Lexicographically compare (source,dest) pair.		int cmp = source.compareTo(other.source);		if (cmp != 0)			return cmp;		cmp = dest.compareTo(other.dest);		if (cmp != 0)			return cmp;		return type - other.type;	}