| 1 | package graphutil |
| 2 | |
| 3 | import ( |
| 4 | "fmt" |
| 5 | |
| 6 | "github.com/dominikbraun/graph" |
| 7 | |
| 8 | "go.bigb.es/auxilia/collect" |
| 9 | "go.bigb.es/auxilia/collect/set" |
| 10 | ) |
| 11 | |
| 12 | // Roots returns a list of all vertices that have no incoming edges. |
| 13 | func Roots[K comparable, T any](g graph.Graph[K, T]) []K { |
| 14 | roots := make([]K, 0) |
| 15 | |
| 16 | pMap, err := g.PredecessorMap() |
| 17 | if err != nil { |
| 18 | return roots |
| 19 | } |
| 20 | |
| 21 | for vertex := range pMap { |
| 22 | if len(pMap[vertex]) == 0 { |
| 23 | roots = append(roots, vertex) |
| 24 | } |
| 25 | } |
| 26 | |
| 27 | return roots |
| 28 | } |
| 29 | |
| 30 | func RecursiveDFSAfter[K comparable, T any](g graph.Graph[K, T], start K, visit func(K)) error { |
| 31 | adjacencyMap, err := g.AdjacencyMap() |
| 32 | if err != nil { |
| 33 | return fmt.Errorf("could not get adjacency map: %w", err) |
| 34 | } |
| 35 | |
| 36 | if _, ok := adjacencyMap[start]; !ok { |
| 37 | return fmt.Errorf("could not find start vertex with hash %v", start) |
| 38 | } |
| 39 | |
| 40 | vertices, err := g.Order() |
| 41 | if err != nil { |
| 42 | return fmt.Errorf("could not get number of vertices: %w", err) |
| 43 | } |
| 44 | nodeMark := set.NewSet[K](vertices) |
| 45 | |
| 46 | var recursiveCall func(hash K) |
| 47 | |
| 48 | recursiveCall = func(hash K) { |
| 49 | if !nodeMark.Add(hash) { |
| 50 | return |
| 51 | } |
| 52 | |
| 53 | for adjacency := range adjacencyMap[hash] { |
| 54 | recursiveCall(adjacency) |
| 55 | } |
| 56 | |
| 57 | visit(hash) |
| 58 | } |
| 59 | |
| 60 | recursiveCall(start) |
| 61 | |
| 62 | return nil |
| 63 | } |
| 64 | |
| 65 | func ChronologicalSort[K comparable, T any](g graph.Graph[K, T]) ([]K, error) { |
| 66 | roots := Roots(g) |
| 67 | |
| 68 | if len(roots) == 0 { |
| 69 | return nil, fmt.Errorf("graph has no roots") |
| 70 | } |
| 71 | |
| 72 | vertices, err := g.Order() |
| 73 | if err != nil { |
| 74 | return nil, fmt.Errorf("could not get number of vertices: %w", err) |
| 75 | } |
| 76 | order := make([]K, 0, vertices) |
| 77 | |
| 78 | for _, root := range roots { |
| 79 | if err := RecursiveDFSAfter(g, root, func(hash K) { |
| 80 | order = append(order, hash) |
| 81 | }); err != nil { |
| 82 | return nil, fmt.Errorf("could not perform DFS: %w", err) |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | return collect.UniqueComparableOrdered(order), nil |
| 87 | } |
| 88 | |