Borůvka's Algorithm — Parallel-Friendly MST

List boruvka(int V, List edges) {
  UnionFind uf = new UnionFind(V);
  List mst = new ArrayList<>();
  int components = V;
  while (components > 1) {
    Edge[] cheapest = new Edge[V];
    for (Edge e : edges) {
      int cu = uf.find(e.u), cv = uf.find(e.v);
      if (cu == cv) continue;
      if (cheapest[cu] == null || e.w < cheapest[cu].w) cheapest[cu] = e;
      if (cheapest[cv] == null || e.w < cheapest[cv].w) cheapest[cv] = e;
    }
    for (Edge e : cheapest)
      if (e != null && uf.union(e.u, e.v)) {
        mst.add(e); components--;
      }
  }
  return mst;
}