Move binomial_tree_graph generator to rustworkx-core (#781)

* Initial bi tree

* Start rework

* First tests

* Finish tests

* Clippy

rustworkx-core/src/generators/binomial_tree_graph.rs

@@ -0,0 +1,247 @@
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+
+use petgraph::data::{Build, Create};
+use petgraph::visit::{Data, EdgeRef, GraphBase, IntoEdgeReferences, NodeIndexable};
+
+use super::InvalidInputError;
+
+/// Generate a binomial tree graph
+///
+/// Arguments:
+///
+/// * `order` - The order of the binomial tree.
+/// * `weights` - A `Vec` of node weight objects. If the number of weights is
+///     less than 2**order extra nodes with None will be appended.
+/// * `default_node_weight` - A callable that will return the weight to use
+///     for newly created nodes. This is ignored if `weights` is specified,
+///     as the weights from that argument will be used instead.
+/// * `default_edge_weight` - A callable that will return the weight object
+///     to use for newly created edges.
+/// * `bidirectional` - Whether edges are added bidirectionally, if set to
+///     `true` then for any edge `(u, v)` an edge `(v, u)` will also be added.
+///     If the graph is undirected this will result in a pallel edge.
+///
+/// # Example
+/// ```rust
+/// use rustworkx_core::petgraph;
+/// use rustworkx_core::generators::binomial_tree_graph;
+/// use rustworkx_core::petgraph::visit::EdgeRef;
+///
+/// let expected_edge_list = vec![
+///     (0, 1),
+///     (2, 3),
+///     (0, 2),
+///     (4, 5),
+///     (6, 7),
+///     (4, 6),
+///     (0, 4),
+///     (8, 9),
+///     (10, 11),
+///     (8, 10),
+///     (12, 13),
+///     (14, 15),
+///     (12, 14),
+///     (8, 12),
+///     (0, 8),
+/// ];
+/// let g: petgraph::graph::UnGraph<(), ()> = binomial_tree_graph(
+///     4,
+///     None,
+///     || {()},
+///     || {()},
+///     false
+/// ).unwrap();
+/// assert_eq!(
+///     expected_edge_list,
+///     g.edge_references()
+///         .map(|edge| (edge.source().index(), edge.target().index()))
+///         .collect::<Vec<(usize, usize)>>(),
+/// )
+/// ```
+pub fn binomial_tree_graph<G, T, F, H, M>(
+    order: u32,
+    weights: Option<Vec<T>>,
+    mut default_node_weight: F,
+    mut default_edge_weight: H,
+    bidirectional: bool,
+) -> Result<G, InvalidInputError>
+where
+    G: Build + Create + Data<NodeWeight = T, EdgeWeight = M> + NodeIndexable,
+    for<'b> &'b G: GraphBase<NodeId = G::NodeId> + IntoEdgeReferences + Copy,
+    F: FnMut() -> T,
+    H: FnMut() -> M,
+    T: Clone,
+{
+    if order >= 60 {
+        return Err(InvalidInputError {});
+    }
+    let num_nodes = usize::pow(2, order);
+    let num_edges = usize::pow(2, order) - 1;
+    let mut graph = G::with_capacity(num_nodes, num_edges);
+
+    for i in 0..num_nodes {
+        match weights {
+            Some(ref weights) => {
+                if weights.len() > num_nodes {
+                    return Err(InvalidInputError {});
+                }
+                if i < weights.len() {
+                    graph.add_node(weights[i].clone())
+                } else {
+                    graph.add_node(default_node_weight())
+                }
+            }
+            None => graph.add_node(default_node_weight()),
+        };
+    }
+
+    fn find_edge<G>(graph: &mut G, source: usize, target: usize) -> bool
+    where
+        G: NodeIndexable,
+        for<'b> &'b G: GraphBase<NodeId = G::NodeId> + IntoEdgeReferences,
+    {
+        let mut found = false;
+        for edge in graph.edge_references() {
+            if graph.to_index(edge.source()) == source && graph.to_index(edge.target()) == target {
+                found = true;
+                break;
+            }
+        }
+        found
+    }
+
+    let mut n = 1;
+    let zero_index = 0;
+    for _ in 0..order {
+        let edges: Vec<(usize, usize)> = graph
+            .edge_references()
+            .map(|e| (graph.to_index(e.source()), graph.to_index(e.target())))
+            .collect();
+
+        for (source, target) in edges {
+            let source_index = source + n;
+            let target_index = target + n;
+
+            if !find_edge(&mut graph, source_index, target_index) {
+                graph.add_edge(
+                    graph.from_index(source_index),
+                    graph.from_index(target_index),
+                    default_edge_weight(),
+                );
+            }
+            if bidirectional && !find_edge(&mut graph, target_index, source_index) {
+                graph.add_edge(
+                    graph.from_index(target_index),
+                    graph.from_index(source_index),
+                    default_edge_weight(),
+                );
+            }
+        }
+        if !find_edge(&mut graph, zero_index, n) {
+            graph.add_edge(
+                graph.from_index(zero_index),
+                graph.from_index(n),
+                default_edge_weight(),
+            );
+        }
+        if bidirectional && !find_edge(&mut graph, n, zero_index) {
+            graph.add_edge(
+                graph.from_index(n),
+                graph.from_index(zero_index),
+                default_edge_weight(),
+            );
+        }
+        n *= 2;
+    }
+    Ok(graph)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::generators::binomial_tree_graph;
+    use crate::generators::InvalidInputError;
+    use crate::petgraph;
+    use crate::petgraph::visit::EdgeRef;
+
+    #[test]
+    fn test_binomial_tree_graph() {
+        let expected_edge_list = vec![
+            (0, 1),
+            (2, 3),
+            (0, 2),
+            (4, 5),
+            (6, 7),
+            (4, 6),
+            (0, 4),
+            (8, 9),
+            (10, 11),
+            (8, 10),
+            (12, 13),
+            (14, 15),
+            (12, 14),
+            (8, 12),
+            (0, 8),
+        ];
+        let g: petgraph::graph::UnGraph<(), ()> =
+            binomial_tree_graph(4, None, || (), || (), false).unwrap();
+        assert_eq!(
+            expected_edge_list,
+            g.edge_references()
+                .map(|edge| (edge.source().index(), edge.target().index()))
+                .collect::<Vec<(usize, usize)>>(),
+        );
+    }
+
+    #[test]
+    fn test_directed_binomial_tree_graph() {
+        let expected_edge_list = vec![
+            (0, 1),
+            (2, 3),
+            (0, 2),
+            (4, 5),
+            (6, 7),
+            (4, 6),
+            (0, 4),
+            (8, 9),
+            (10, 11),
+            (8, 10),
+            (12, 13),
+            (14, 15),
+            (12, 14),
+            (8, 12),
+            (0, 8),
+        ];
+        let g: petgraph::graph::DiGraph<(), ()> =
+            binomial_tree_graph(4, None, || (), || (), false).unwrap();
+        assert_eq!(
+            expected_edge_list,
+            g.edge_references()
+                .map(|edge| (edge.source().index(), edge.target().index()))
+                .collect::<Vec<(usize, usize)>>(),
+        );
+    }
+
+    #[test]
+    fn test_binomial_tree_error() {
+        match binomial_tree_graph::<petgraph::graph::DiGraph<(), ()>, (), _, _, ()>(
+            75,
+            None,
+            || (),
+            || (),
+            false,
+        ) {
+            Ok(_) => panic!("Returned a non-error"),
+            Err(e) => assert_eq!(e, InvalidInputError),
+        };
+    }
+}

rustworkx-core/src/generators/mod.rs

@@ -12,6 +12,7 @@
 
 //! This module contains generator functions for building graphs
 
+mod binomial_tree_graph;
 mod cycle_graph;
 mod grid_graph;
 mod heavy_hex_graph;
@@ -38,6 +39,7 @@ impl fmt::Display for InvalidInputError {
     }
 }
 
+pub use binomial_tree_graph::binomial_tree_graph;
 pub use cycle_graph::cycle_graph;
 pub use grid_graph::grid_graph;
 pub use heavy_hex_graph::heavy_hex_graph;