toFlag.retainAll(flagLocs.asSet());
}
}
return;
} else if(bombsToPlace < 0 || bombsToPlace > unknown.size()) return;
Position p = unknown.remove(0);
enumerateBombLocations(helper,board,new ArrayList<>(unknown),new Node(p,flagLocs), pickLocs, bombsToPlace-1);
enumerateBombLocations(helper,board,new ArrayList<>(unknown),flagLocs, new Node(p,pickLocs), bombsToPlace);
}