Initial data commit

Task/Dijkstras-algorithm/OCaml/dijkstras-algorithm-2.ocaml

@@ -0,0 +1,56 @@
+type vertex = int
+type weight = float
+type neighbor = vertex * weight
+module VertexSet = Set.Make(struct type t = weight * vertex let compare = compare end)
+
+let dijkstra (src:vertex) (adj_list:neighbor list array) : weight array * vertex array =
+  let n = Array.length adj_list in
+  let min_distance = Array.make n infinity in
+  min_distance.(src) <- 0.;
+  let previous = Array.make n (-1) in
+  let rec aux vertex_queue =
+    if not (VertexSet.is_empty vertex_queue) then
+      let dist, u = VertexSet.min_elt vertex_queue in
+      let vertex_queue' = VertexSet.remove (dist, u) vertex_queue in
+      let edges = adj_list.(u) in
+      let f vertex_queue (v, weight) =
+        let dist_thru_u = dist +. weight in
+        if dist_thru_u >= min_distance.(v) then
+          vertex_queue
+        else begin
+          let vertex_queue' = VertexSet.remove (min_distance.(v), v) vertex_queue in
+          min_distance.(v) <- dist_thru_u;
+          previous.(v) <- u;
+          VertexSet.add (min_distance.(v), v) vertex_queue'
+        end
+      in
+      aux (List.fold_left f vertex_queue' edges)
+  in
+  aux (VertexSet.singleton (min_distance.(src), src));
+  min_distance, previous
+
+let shortest_path_to (target : vertex) (previous : vertex array) : vertex list =
+  let rec aux target acc =
+    if target = -1 then
+      acc
+    else
+      aux previous.(target) (target :: acc)
+  in
+  aux target []
+
+let adj_list =
+  [| [(1, 7.); (2, 9.); (5, 14.)];           (* 0 = a *)
+     [(0, 7.); (2, 10.); (3, 15.)];          (* 1 = b *)
+     [(0, 9.); (1, 10.); (3, 11.); (5, 2.)]; (* 2 = c *)
+     [(1, 15.); (2, 11.); (4, 6.)];          (* 3 = d *)
+     [(3, 6.); (5, 9.)];                     (* 4 = e *)
+     [(0, 14.); (2, 2.); (4, 9.)]            (* 5 = f *)
+  |]
+
+let () =
+  let min_distance, previous = dijkstra 0 adj_list in
+  Printf.printf "Distance from 0 to 4: %f\n" min_distance.(4);
+  let path = shortest_path_to 4 previous in
+  print_string "Path: ";
+  List.iter (Printf.printf "%d, ") path;
+  print_newline ()