func tarjanSort(successors map[bson.ObjectId][]bson.ObjectId) [][]bson.ObjectId {
// http://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm
data := &tarjanData{
successors: successors,
nodes: make([]tarjanNode, 0, len(successors)),
index: make(map[bson.ObjectId]int, len(successors)),
}
for id := range successors {
id := bson.ObjectId(string(id))
if _, seen := data.index[id]; !seen {
data.strongConnect(id)
}
}
// Sort connected components to stabilize the algorithm.
for _, ids := range data.output {
if len(ids) > 1 {
sort.Sort(idList(ids))
}
}
return data.output
}
func bid(n int) bson.ObjectId {
return bson.ObjectId(fmt.Sprintf("%024d", n))
}