Add breadth-first search algorithms and tests
This commit is contained in:
@@ -0,0 +1,253 @@
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#[macro_export]
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macro_rules! bfs_tests {
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($T:ty) => {
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#[test]
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fn bfs_single_vertex() {
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use $crate::traits::GraphTopology;
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let mut graph = <$T>::new();
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let v = graph.add_vertex();
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let result = $crate::algorithms::bfs(&graph, v);
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assert_eq!(
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result.distances[v],
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Some(0),
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"unexpected distance of source vertex"
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);
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assert_eq!(
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result.predecessors[v], None,
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"unexpected predecessor of source vertex"
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);
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}
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#[test]
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fn bfs_disconnected() {
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let (graph, vertices) = make_test_graph_disconnected();
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let result = $crate::algorithms::bfs(&graph, vertices[0]);
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assert_eq!(
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result.distances[vertices[0]],
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Some(0),
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"unexpected distance of source vertex"
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);
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assert_eq!(
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result.predecessors[vertices[0]], None,
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"unexpected predecessor of source vertex"
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);
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for &v in &vertices[1..3] {
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assert_eq!(
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result.distances[v], None,
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"disconnected vertex {v:?} should have no distance"
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);
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assert_eq!(
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result.predecessors[v], None,
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"disconnected vertex {v:?} should have no predecessor"
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);
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}
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}
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#[test]
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fn bfs() {
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let (graph, vertices, _, _) = make_test_graph();
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let result = $crate::algorithms::bfs(&graph, vertices[0]);
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assert_bfs_distances(&result.distances, &vertices);
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assert_bfs_predecessors(&result.predecessors, &vertices);
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}
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#[test]
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fn bfs_distances_single_vertex() {
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use $crate::traits::GraphTopology;
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let mut graph = <$T>::new();
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let v = graph.add_vertex();
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let distances = $crate::algorithms::bfs_distances(&graph, v);
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assert_eq!(
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distances[v],
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Some(0),
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"unexpected distance of source vertex"
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);
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}
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#[test]
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fn bfs_distances_disconnected() {
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let (graph, vertices) = make_test_graph_disconnected();
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let distances = $crate::algorithms::bfs_distances(&graph, vertices[0]);
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assert_eq!(
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distances[vertices[0]],
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Some(0),
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"unexpected distance of source vertex"
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);
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for &v in &vertices[1..3] {
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assert_eq!(
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distances[v], None,
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"disconnected vertex {v:?} should have no distance"
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);
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}
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}
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#[test]
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fn bfs_distances() {
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let (graph, vertices, _, _) = make_test_graph();
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let distances = $crate::algorithms::bfs_distances(&graph, vertices[0]);
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assert_bfs_distances(&distances, &vertices);
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}
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#[test]
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fn bfs_find_source() {
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use $crate::traits::GraphTopology;
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let mut graph = <$T>::new();
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let v = graph.add_vertex();
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assert_eq!(
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$crate::algorithms::bfs_find(&graph, v, v),
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Some(0),
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"source should be found at distance 0"
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);
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}
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#[test]
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fn bfs_find_disconnected() {
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let (graph, vertices) = make_test_graph_disconnected();
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assert_eq!(
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$crate::algorithms::bfs_find(&graph, vertices[0], vertices[1]),
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None,
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"disconnected target should not be found"
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);
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}
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#[test]
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fn bfs_find() {
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let (graph, vertices, _, _) = make_test_graph();
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let expected_distances = [
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Some(0),
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Some(1),
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Some(2),
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Some(2),
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Some(2),
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Some(3),
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Some(3),
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Some(3),
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Some(3),
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Some(4),
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];
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for i in 0..10 {
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assert_eq!(
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$crate::algorithms::bfs_find(&graph, vertices[0], vertices[i]),
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expected_distances[i],
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"unexpected distance from {:?} to {:?}",
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vertices[0],
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vertices[i]
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);
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}
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}
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#[test]
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fn bfs_find_where_source_matches() {
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use $crate::traits::GraphTopology;
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let mut graph = <$T>::new();
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let v = graph.add_vertex();
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let result = $crate::algorithms::bfs_find_where(&graph, v, |u| u == v);
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assert_eq!(result, Some((v, 0)), "source should match with distance 0");
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}
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#[test]
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fn bfs_find_where_disconnected() {
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let (graph, vertices) = make_test_graph_disconnected();
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let target = vertices[1];
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assert_eq!(
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$crate::algorithms::bfs_find_where(&graph, vertices[0], |v| v == target),
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None,
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"disconnected vertex should not be found"
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);
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}
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#[test]
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fn bfs_find_where_no_match() {
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let (graph, vertices, _, _) = make_test_graph();
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assert_eq!(
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$crate::algorithms::bfs_find_where(&graph, vertices[0], |_| false),
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None,
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"no vertex should match an always-false predicate"
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);
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}
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#[test]
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fn bfs_find_where_nearest() {
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let (graph, vertices, _, _) = make_test_graph();
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// vertices[5], vertices[6], vertices[7], vertices[8] are all at distance 3 from vertices[0].
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// vertices[9] is at distance 4. Predicate matches vertices[7], vertices[8], vertices[9].
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// BFS must return one of the distance-3 ones, not vertices[9].
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let result = $crate::algorithms::bfs_find_where(&graph, vertices[0], |v| {
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v == vertices[7] || v == vertices[8] || v == vertices[9]
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});
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assert!(result.is_some(), "expected a match");
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let (found, distance) = result.unwrap();
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assert_eq!(
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distance, 3,
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"unexpected distance to nearest matching vertex {found:?}",
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);
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assert!(
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found == vertices[7] || found == vertices[8],
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"unexpected nearest match vertex {found:?}, should be {:?} or {:?}",
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vertices[7], vertices[8]
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);
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}
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fn assert_bfs_distances(
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distances: &$crate::maps::VertexMap<
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<$T as $crate::traits::GraphTopology>::Vertex,
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Option<u32>,
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>,
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vertices: &[<$T as $crate::traits::GraphTopology>::Vertex],
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) {
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let expected = [
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Some(0),
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Some(1),
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Some(2),
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Some(2),
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Some(2),
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Some(3),
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Some(3),
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Some(3),
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Some(3),
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Some(4),
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];
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for i in 0..10 {
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assert_eq!(
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distances[vertices[i]], expected[i],
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"unexpected BFS distance from {:?} to {:?}",
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vertices[0], vertices[i]
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);
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}
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}
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fn assert_bfs_predecessors(
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predecessors: &$crate::maps::VertexMap<
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<$T as $crate::traits::GraphTopology>::Vertex,
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Option<<$T as $crate::traits::GraphTopology>::Vertex>,
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>,
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vertices: &[<$T as $crate::traits::GraphTopology>::Vertex],
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) {
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assert_eq!(
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predecessors[vertices[0]], None,
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"source should have no predecessor"
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);
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// Each non-source vertex's predecessor must be adjacent and at distance one less.
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let expected_predecessors = [
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vec![None],
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vec![Some(vertices[0])],
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vec![Some(vertices[1])],
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vec![Some(vertices[1])],
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vec![Some(vertices[1])],
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vec![Some(vertices[2])],
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vec![Some(vertices[2]), Some(vertices[3])],
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vec![Some(vertices[4])],
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vec![Some(vertices[4])],
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vec![Some(vertices[5]), Some(vertices[6]), Some(vertices[7])],
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];
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for i in 1..10 {
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assert!(
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expected_predecessors[i].contains(&predecessors[vertices[i]]),
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"unexpected predecessor {:?} of {:?}",
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predecessors[vertices[i]],
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vertices[i]
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);
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}
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}
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};
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}
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