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Graph BFS using Queue + Hashtbl visited-set + List.assoc_opt + List.iter. Returns 6 for a graph where A reaches B/C/D/E/F. Demonstrates 4 stdlib modules (Queue, Hashtbl, List) cooperating in a real algorithm.
44 lines
869 B
OCaml
44 lines
869 B
OCaml
(* Baseline: graph BFS using Queue + Hashtbl visited set.
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Returns the count of reachable nodes. *)
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(* Adjacency as an assoc list of (node, neighbors). *)
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let graph =
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[ ("A", ["B"; "C"])
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; ("B", ["D"])
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; ("C", ["D"; "E"])
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; ("D", ["F"])
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; ("E", ["F"])
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; ("F", [])
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]
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;;
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let neighbors n =
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match List.assoc_opt n graph with
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| None -> []
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| Some ns -> ns
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;;
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let bfs start =
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let visited = Hashtbl.create 16 in
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let q = Queue.create () in
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Queue.push start q ;
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Hashtbl.add visited start true ;
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let rec loop () =
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if Queue.is_empty q then ()
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else
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let v = Queue.pop q in
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List.iter
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(fun n ->
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if not (Hashtbl.mem visited n) then begin
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Hashtbl.add visited n true ;
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Queue.push n q
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end)
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(neighbors v) ;
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loop ()
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in
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loop () ;
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Hashtbl.length visited
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;;
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bfs "A"
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