private void prim(int s, StringBuilder sb) {
distTo[s] = 0;
pq.insert(s, distTo[s]);
while (!pq.isEmpty()) {
int v = pq.delMin();
if (v != s) {
Route r = edgeTo[v];
String str = String.format("%s, %s : %d\n", r.fst(), r.snd(), r.distance());
sb.append(str);
}
scan(v);
}
}
