@@ -28,26 +28,26 @@ concept edge_weight_function2 = // e.g. weight(uv)
2828 basic_edge_weight_function2<G, WF, Distance, less<range_value_t <Distance>>, plus<range_value_t <Distance>>>;
2929
3030
31- class null_range_type : public std ::vector<size_t > {
31+ class _null_range_type : public std ::vector<size_t > {
3232 using T = size_t ;
3333 using Allocator = std::allocator<T>;
3434 using Base = std::vector<T, Allocator>;
3535
3636public:
37- null_range_type () noexcept (noexcept (Allocator())) = default ;
38- explicit null_range_type (const Allocator& alloc) noexcept {}
39- null_range_type (Base::size_type count, const T& value, const Allocator& alloc = Allocator()) {}
40- explicit null_range_type (Base::size_type count, const Allocator& alloc = Allocator()) {}
37+ _null_range_type () noexcept (noexcept (Allocator())) = default ;
38+ explicit _null_range_type (const Allocator& alloc) noexcept {}
39+ _null_range_type (Base::size_type count, const T& value, const Allocator& alloc = Allocator()) {}
40+ explicit _null_range_type (Base::size_type count, const Allocator& alloc = Allocator()) {}
4141 template <class InputIt >
42- null_range_type (InputIt first, InputIt last, const Allocator& alloc = Allocator()) {}
43- null_range_type (const null_range_type & other) : Base() {}
44- null_range_type (const null_range_type & other, const Allocator& alloc) {}
45- null_range_type (null_range_type && other) noexcept {}
46- null_range_type (null_range_type && other, const Allocator& alloc) {}
47- null_range_type (std::initializer_list<T> init, const Allocator& alloc = Allocator()) {}
42+ _null_range_type (InputIt first, InputIt last, const Allocator& alloc = Allocator()) {}
43+ _null_range_type (const _null_range_type & other) : Base() {}
44+ _null_range_type (const _null_range_type & other, const Allocator& alloc) {}
45+ _null_range_type (_null_range_type && other) noexcept {}
46+ _null_range_type (_null_range_type && other, const Allocator& alloc) {}
47+ _null_range_type (std::initializer_list<T> init, const Allocator& alloc = Allocator()) {}
4848};
4949
50- inline static null_range_type null_predecessors;
50+ inline static _null_range_type null_predecessors;
5151
5252
5353template <class ... Ts>
@@ -80,6 +80,9 @@ constexpr auto print_types(Ts...) {
8080 * The edge weight function must not throw an exception.
8181 * The edge weight function must not modify the graph, the edge, or the vertex (nor any of their associated data).
8282 */
83+
84+ #if 1 // not using Identifiers (original)
85+
8386template <adjacency_list G,
8487 random_access_range Distance,
8588 random_access_range Predecessor,
@@ -101,7 +104,7 @@ void dijkstra_clrs(
101104
102105 // Remark(Andrew): Do we want to allow null distance? What about if both are null? Still run algorithm at all?
103106
104- size_t N (size ( vertices ( g))); // Question(Andrew): Do we want a num_vertices(g) CPO?
107+ size_t N (num_vertices ( g));
105108 assert (seed < N && seed >= 0 );
106109
107110 std::ranges::fill (distance, std::numeric_limits<weight_type>::max ());
@@ -129,12 +132,68 @@ void dijkstra_clrs(
129132 // weight_type w = weight(uv);
130133 if (distance[uid] + w < distance[vid]) {
131134 distance[vid] = distance[uid] + w;
132- if constexpr (!is_same_v<Predecessor, null_range_type>)
135+ if constexpr (!is_same_v<Predecessor, _null_range_type>)
136+ predecessor[vid] = uid;
137+ Q.push ({vid, distance[vid]});
138+ }
139+ }
140+ }
141+ }
142+
143+ #else // using Identifiers
144+
145+ template <adjacency_list G,
146+ random_access_range Distance,
147+ random_access_range Predecessor,
148+ class WF = function<range_value_t<Distance>(edge_identifier_t<G>)>>
149+ requires random_access_range<vertex_range_t<G>> && //
150+ integral<vertex_id_t<G>> && //
151+ is_arithmetic_v<range_value_t<Distance>> && //
152+ convertible_to<vertex_id_t<G>, range_value_t<Predecessor>> && //
153+ edge_weight_function<G, WF>
154+ void dijkstra_clrs(
155+ G&& g, // graph
156+ vertex_identifier_t<G> seed, // starting vertex_id
157+ Distance& distance, // out: distance[uid] of uid from seed
158+ Predecessor& predecessor, // out: predecessor[uid] of uid in path
159+ WF&& weight = [](edge_identifier_t<G> uv) { return range_value_t<Distance>(1); }) // default weight(uv) -> 1
160+ {
161+ using id_type = vertex_id_t<G>;
162+ using weight_type = invoke_result_t<WF, edge_identifer_t<G>>;
163+ const id_type seed_id = vertex_id(g, seed);
164+
165+ size_t N(num_vertices(g));
166+ assert(seed_id < N && seed_id >= 0);
167+
168+ std::ranges::fill(distance, std::numeric_limits<weight_type>::max());
169+ distance[seed_id] = 0;
170+
171+ struct weighted_vertex {
172+ id_type vertex_id = id_type();
173+ weight_type weight = weight_type();
174+ };
175+
176+ using q_compare = decltype([](const weighted_vertex& a, const weighted_vertex& b) { return a.weight > b.weight; });
177+ std::priority_queue<weighted_vertex, std::vector<weighted_vertex>, q_compare> Q;
178+
179+ Q.push({seed_id, distance[seed_id]});
180+
181+ while (!Q.empty()) {
182+ auto uid = Q.top().vertex_id;
183+ Q.pop();
184+
185+ for (auto&& [v_identifier, uv_identifier, w] : views::incidence(g, find_vertex(g, uid), weight)) {
186+ id_type vid = vertex_id(v_identifier);
187+ if (distance[uid] + w < distance[vid]) {
188+ distance[vid] = distance[uid] + w;
189+ if constexpr (!is_same_v<Predecessor, _null_range_type>)
133190 predecessor[vid] = uid;
134191 Q.push({vid, distance[vid]});
135192 }
136193 }
137194 }
138195}
139196
197+ endif // Identifiers
198+
140199} // namespace graph
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