Add generators::complete, without tests

src/generators.rs

@@ -84,6 +84,28 @@ pub fn cycle<G: GraphTopologyAddition>(graph: &mut G, n: usize) -> (Vec<G::Verte
     (vertices, edges)
 }
 
+/// Generates a complete graph.
+///
+/// Generates a [complete graph] *K(n)* with `n` vertices and `n * (n - 1) / 2` edges in `graph` as
+/// a new connected component and returns the new vertices and edges.
+///
+/// For `n == 0`, nothing is added. For `n == 1`, only a single vertex is added.
+///
+/// [Complete graph]: https://en.wikipedia.org/wiki/Complete_graph
+pub fn complete<G: GraphTopologyAddition>(graph: &mut G, n: usize) -> (Vec<G::Vertex>, Vec<G::Edge>) {
+    let capacity = n * (n - 1) / 2;
+    graph.reserve_vertices(n);
+    graph.reserve_edges(capacity);
+    let vertices: Vec<_> = (0..n).map(|_| graph.add_vertex()).collect();
+    let mut edges = Vec::with_capacity(capacity);
+    for (i, &u) in vertices.iter().enumerate() {
+        for &v in &vertices[i + 1..] {
+            edges.push(graph.add_edge(u, v));
+        }
+    }
+    (vertices, edges)
+}
+
 /// Generates a Petersen graph.
 ///
 /// Generates a [Petersen graph] in `graph` as a new connected component and returns the new