Initial release #1
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use std::cmp::Ordering;
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use std::collections::BinaryHeap;
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use crate::models::Graph;
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use crate::models::Vertex;
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#[derive(PartialEq, Eq)]
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struct DistanceOrderedVertex {
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distance: u32,
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vertex: Vertex,
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}
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impl PartialOrd for DistanceOrderedVertex {
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fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
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Some(self.distance.cmp(&other.distance))
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}
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}
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impl Ord for DistanceOrderedVertex {
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fn cmp(&self, other: &Self) -> Ordering {
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other.distance.cmp(&self.distance)
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}
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}
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// TODO: Maybe introduce a return struct type for Dijkstra's algorithm?
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// TODO: Maybe variant of Dijkstra's algorithm without predecessors?
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pub fn dijkstra(graph: &Graph, source: Vertex) -> (Vec<Option<u32>>, Vec<Option<Vertex>>) {
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let mut distances = vec![None; graph.vertex_count()];
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let mut predecessors = vec![None; graph.vertex_count()];
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let mut heap = BinaryHeap::new();
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distances[source.0] = Some(0);
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heap.push(DistanceOrderedVertex {
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vertex: source,
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distance: 0,
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});
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while let Some(v) = heap.pop() {
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// TODO: Simplify with a neighbor iterator.
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// Finds the first neighbor of v.
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let Some(mut incidence) = graph.incidence_headers[v.vertex.0].first_incidence else {
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break;
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};
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loop {
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// Processes one neighbor of v.
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let neighbor = graph.incidence_vertices[incidence.0];
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// TODO: Add a way to provide custom edge weights for Dijkstra's algorithm.
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let edge_weight = 1;
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let new_distance = distances[v.vertex.0].unwrap() + edge_weight;
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if match distances[neighbor.0] {
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None => true,
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Some(old_distance) if old_distance > new_distance => true,
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_ => false,
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} {
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distances[neighbor.0] = Some(new_distance);
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predecessors[neighbor.0] = Some(v.vertex);
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heap.push(DistanceOrderedVertex {
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vertex: neighbor,
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distance: new_distance,
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});
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}
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// Finds next neighbor of v.
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let Some(next) = graph.next_incidences[incidence.0] else {
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break;
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};
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incidence = next;
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}
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}
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(distances, predecessors)
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}
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+5
-145
@@ -1,148 +1,8 @@
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use std::cmp::Ordering;
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use std::collections::BinaryHeap;
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mod algorithms;
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mod models;
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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struct Vertex(usize);
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#[derive(Copy, Clone, PartialEq, Eq)]
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struct Incidence(usize);
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struct VertexIncidenceHeader {
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incidence_count: usize,
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first_incidence: Option<Incidence>,
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}
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// TODO: Visibility of Graph members.
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struct Graph {
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// TODO: Index 'incidence_headers' by a 'Vertex' instead of 'Vertex.0'?
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incidence_headers: Vec<VertexIncidenceHeader>,
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next_incidences: Vec<Option<Incidence>>,
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incidence_vertices: Vec<Vertex>,
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}
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// TODO: Add iterator of vertices.
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// TODO: Add iterator of edges.
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// TODO: Add iterator of vertex neighbors, see 'fn add_adjacent()'.
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impl Graph {
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fn vertex_count(&self) -> usize {
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self.incidence_headers.len()
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}
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fn edge_count(&self) -> usize {
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self.next_incidences.len() / 2
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}
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fn degree(&self, v: Vertex) -> usize {
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self.incidence_headers[v.0].incidence_count
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}
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// TODO: 'fn are_adjacent()' could probably be done with a neighbor vertex iterator.
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fn are_adjacent(&self, v1: Vertex, v2: Vertex) -> bool {
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let Some(mut incidence) = self.incidence_headers[v1.0].first_incidence else {
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return false;
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};
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loop {
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if self.incidence_vertices[incidence.0] == v2 {
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return true;
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}
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let Some(next) = self.next_incidences[incidence.0] else {
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return false;
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};
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incidence = next;
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}
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}
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// TODO: 'fn add_vertex()' should not be publicly accessible for all graph implementations.
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// TODO: 'fn add_vertex()' needs variants for custom vertex data.
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fn add_vertex(&mut self) -> Vertex {
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self.incidence_headers.push(VertexIncidenceHeader {
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incidence_count: 0,
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first_incidence: None,
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});
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Vertex(self.incidence_headers.len() - 1)
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}
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// TODO: 'fn add_edge()' should not be publicly accessible for all graph implementations.
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// TODO: 'fn add_edge()' needs variants for custom edge data.
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fn add_edge(&mut self, v1: Vertex, v2: Vertex) {
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self.add_incidence(v1, v2);
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self.add_incidence(v2, v1);
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}
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fn add_incidence(&mut self, v1: Vertex, v2: Vertex) {
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self.incidence_vertices.push(v2);
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self.next_incidences
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.push(self.incidence_headers[v1.0].first_incidence.take());
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self.incidence_headers[v1.0].incidence_count += 1;
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self.incidence_headers[v1.0].first_incidence =
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Some(Incidence(self.incidence_vertices.len() - 1));
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}
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}
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#[derive(PartialEq, Eq)]
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struct DistanceOrderedVertex {
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distance: u32,
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vertex: Vertex,
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}
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impl PartialOrd for DistanceOrderedVertex {
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fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
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Some(self.distance.cmp(&other.distance))
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}
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}
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impl Ord for DistanceOrderedVertex {
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fn cmp(&self, other: &Self) -> Ordering {
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other.distance.cmp(&self.distance)
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}
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}
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// TODO: Maybe introduce a return struct type for Dijkstra's algorithm?
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// TODO: Maybe variant of Dijkstra's algorithm without predecessors?
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fn dijkstra(graph: &Graph, source: Vertex) -> (Vec<Option<u32>>, Vec<Option<Vertex>>) {
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let mut distances = vec![None; graph.vertex_count()];
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let mut predecessors = vec![None; graph.vertex_count()];
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let mut heap = BinaryHeap::new();
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distances[source.0] = Some(0);
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heap.push(DistanceOrderedVertex {
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vertex: source,
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distance: 0,
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});
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while let Some(v) = heap.pop() {
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// TODO: Simplify with a neighbor iterator.
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// Finds the first neighbor of v.
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let Some(mut incidence) = graph.incidence_headers[v.vertex.0].first_incidence else {
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break;
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};
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loop {
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// Processes one neighbor of v.
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let neighbor = graph.incidence_vertices[incidence.0];
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// TODO: Add a way to provide custom edge weights for Dijkstra's algorithm.
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let edge_weight = 1;
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let new_distance = distances[v.vertex.0].unwrap() + edge_weight;
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if match distances[neighbor.0] {
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None => true,
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Some(old_distance) if old_distance > new_distance => true,
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_ => false,
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} {
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distances[neighbor.0] = Some(new_distance);
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predecessors[neighbor.0] = Some(v.vertex);
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heap.push(DistanceOrderedVertex {
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vertex: neighbor,
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distance: new_distance,
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});
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}
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// Finds next neighbor of v.
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let Some(next) = graph.next_incidences[incidence.0] else {
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break;
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};
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incidence = next;
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}
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}
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(distances, predecessors)
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}
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use models::Graph;
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use models::Vertex;
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fn main() {
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// TODO: Move this graph example into one or more tests.
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@@ -221,7 +81,7 @@ fn main() {
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);
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}
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let (distances, predecessors) = dijkstra(&graph, vertices[0]);
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let (distances, predecessors) = algorithms::dijkstra(&graph, vertices[0]);
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let expected_distances_from_v0 = [
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Some(0),
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Some(1),
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@@ -0,0 +1,81 @@
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// TODO: Vertex value must not be public.
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub struct Vertex(pub usize);
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// TODO: Incidence value must not be public.
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// TODO: Incidence must not be public.
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#[derive(Copy, Clone, PartialEq, Eq)]
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pub struct Incidence(pub usize);
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// TODO: VertexIncidenceHeader and its fields must not be public, but without iterators there is currently no other way to access vertex incidences.
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pub struct VertexIncidenceHeader {
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incidence_count: usize,
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pub first_incidence: Option<Incidence>,
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}
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// TODO: Graph fields must not be public.
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pub struct Graph {
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// TODO: Index 'incidence_headers' by a 'Vertex' instead of 'Vertex.0'?
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pub incidence_headers: Vec<VertexIncidenceHeader>,
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pub next_incidences: Vec<Option<Incidence>>,
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pub incidence_vertices: Vec<Vertex>,
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}
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// TODO: Add iterator of vertices.
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// TODO: Add iterator of edges.
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// TODO: Add iterator of vertex neighbors, see 'fn add_adjacent()'.
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impl Graph {
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pub fn vertex_count(&self) -> usize {
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self.incidence_headers.len()
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}
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pub fn edge_count(&self) -> usize {
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self.next_incidences.len() / 2
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}
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pub fn degree(&self, v: Vertex) -> usize {
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self.incidence_headers[v.0].incidence_count
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}
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// TODO: 'fn are_adjacent()' could probably be done with a neighbor vertex iterator.
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pub fn are_adjacent(&self, v1: Vertex, v2: Vertex) -> bool {
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let Some(mut incidence) = self.incidence_headers[v1.0].first_incidence else {
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return false;
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};
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loop {
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if self.incidence_vertices[incidence.0] == v2 {
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return true;
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}
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let Some(next) = self.next_incidences[incidence.0] else {
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return false;
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};
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incidence = next;
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}
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}
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// TODO: 'fn add_vertex()' should not be publicly accessible for all graph implementations.
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// TODO: 'fn add_vertex()' needs variants for custom vertex data.
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pub fn add_vertex(&mut self) -> Vertex {
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self.incidence_headers.push(VertexIncidenceHeader {
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incidence_count: 0,
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first_incidence: None,
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});
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Vertex(self.incidence_headers.len() - 1)
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}
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// TODO: 'fn add_edge()' should not be publicly accessible for all graph implementations.
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// TODO: 'fn add_edge()' needs variants for custom edge data.
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pub fn add_edge(&mut self, v1: Vertex, v2: Vertex) {
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self.add_incidence(v1, v2);
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self.add_incidence(v2, v1);
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}
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fn add_incidence(&mut self, v1: Vertex, v2: Vertex) {
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self.incidence_vertices.push(v2);
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self.next_incidences
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.push(self.incidence_headers[v1.0].first_incidence.take());
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self.incidence_headers[v1.0].incidence_count += 1;
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self.incidence_headers[v1.0].first_incidence =
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Some(Incidence(self.incidence_vertices.len() - 1));
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}
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}
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Reference in New Issue
Block a user