diff --git a/src/graph/dag.rs b/src/graph/dag.rs
index 5a70142..df634bc 100644
--- a/src/graph/dag.rs
+++ b/src/graph/dag.rs
@@ -13,8 +13,8 @@ where
         DirectedAcyclicGraph(AdjacencyGraph::new())
     }
 
-    fn to_adjecency_graph(&self) -> AdjacencyGraph<V> {
-        self.0.clone()
+    fn to_adjecency_graph(&self) -> &AdjacencyGraph<V> {
+        &self.0
     }
 
     fn nodes(&self) -> BTreeSet<V> {
diff --git a/src/graph/directed.rs b/src/graph/directed.rs
index 93bb4e8..fb0dac5 100644
--- a/src/graph/directed.rs
+++ b/src/graph/directed.rs
@@ -21,8 +21,8 @@ where
         }
     }
 
-    fn to_adjecency_graph(&self) -> AdjacencyGraph<V> {
-        self.clone()
+    fn to_adjecency_graph(&self) -> &AdjacencyGraph<V> {
+        &self
     }
 
     fn nodes(&self) -> BTreeSet<V> {
@@ -103,9 +103,7 @@ where
             undirected.add_edge(to.clone(), from.clone());
         }
 
-        UndirectedGraph {
-            directed: undirected,
-        }
+        UndirectedGraph(undirected)
     }
 
     pub fn has_edge(&self, from: &V, to: &V) -> bool {
diff --git a/src/graph/mod.rs b/src/graph/mod.rs
index 15821a8..18ce52d 100644
--- a/src/graph/mod.rs
+++ b/src/graph/mod.rs
@@ -24,7 +24,7 @@ where
         graph
     }
 
-    fn to_adjecency_graph(&self) -> AdjacencyGraph<V>;
+    fn to_adjecency_graph(&self) -> &AdjacencyGraph<V>;
 
     fn nodes(&self) -> BTreeSet<V>;
     fn adjacencies(&self) -> BTreeMap<V, BTreeSet<V>>;
@@ -65,16 +65,13 @@ where
     adjacencies: BTreeMap<V, BTreeSet<V>>,
 }
 
-#[derive(Debug)]
-pub struct UndirectedGraph<V>
+#[derive(Debug, Clone)]
+pub struct UndirectedGraph<V>(AdjacencyGraph<V>)
 where
-    V: Clone,
-{
-    pub directed: AdjacencyGraph<V>,
-}
+    V: Clone;
 
-#[derive(Debug)]
-pub struct DirectedAcyclicGraph<V>(pub AdjacencyGraph<V>)
+#[derive(Debug, Clone)]
+pub struct DirectedAcyclicGraph<V>(AdjacencyGraph<V>)
 where
     V: Clone;
 
diff --git a/src/graph/undirected.rs b/src/graph/undirected.rs
index fda9a4e..e0f198b 100644
--- a/src/graph/undirected.rs
+++ b/src/graph/undirected.rs
@@ -15,47 +15,45 @@ where
     where
         Self: Sized,
     {
-        UndirectedGraph {
-            directed: AdjacencyGraph::new(),
-        }
+        UndirectedGraph(AdjacencyGraph::new())
     }
 
-    fn to_adjecency_graph(&self) -> AdjacencyGraph<V> {
-        self.directed.clone()
+    fn to_adjecency_graph(&self) -> &AdjacencyGraph<V> {
+        &self.0
     }
 
     fn nodes(&self) -> BTreeSet<V> {
-        self.directed.nodes()
+        self.0.nodes()
     }
 
     fn adjacencies(&self) -> BTreeMap<V, BTreeSet<V>> {
-        self.directed.adjacencies()
+        self.0.adjacencies()
     }
 
     fn neighbors(&self, from: &V) -> BTreeSet<V> {
-        self.directed.neighbors(from)
+        self.0.neighbors(from)
     }
 
     fn edges(&self) -> BTreeSet<(V, V)> {
-        self.directed.edges()
+        self.0.edges()
     }
 
     fn add_node(&mut self, node: V) {
-        self.directed.add_node(node);
+        self.0.add_node(node);
     }
 
     fn add_edge(&mut self, from: V, to: V) {
-        self.directed.add_edge(from.clone(), to.clone());
-        self.directed.add_edge(to, from);
+        self.0.add_edge(from.clone(), to.clone());
+        self.0.add_edge(to, from);
     }
 
     fn remove_node(&mut self, node: &V) {
-        self.directed.remove_node(node);
+        self.0.remove_node(node);
     }
 
     fn remove_edge(&mut self, from: &V, to: &V) {
-        self.directed.remove_edge(from, to);
-        self.directed.remove_edge(to, from);
+        self.0.remove_edge(from, to);
+        self.0.remove_edge(to, from);
     }
 }
 
@@ -64,22 +62,22 @@ where
     V: Ord + Eq + Clone + Debug,
 {
     pub fn add_edge(&mut self, from: V, to: V) {
-        self.directed.add_edge(from.clone(), to.clone());
-        self.directed.add_edge(to.clone(), from.clone());
+        self.0.add_edge(from.clone(), to.clone());
+        self.0.add_edge(to.clone(), from.clone());
     }
 
     pub fn remove_edge(&mut self, from: &V, to: &V) {
-        self.directed.remove_edge(from, to);
-        self.directed.remove_edge(to, from);
+        self.0.remove_edge(from, to);
+        self.0.remove_edge(to, from);
     }
 
     pub fn connected_components(&self) -> Vec<Vec<V>> {
         let mut visited = BTreeSet::new();
         let mut result = Vec::new();
 
-        let pb = ProgressBar::new(self.directed.nodes.len() as u64);
+        let pb = ProgressBar::new(self.0.nodes.len() as u64);
 
-        for node in self.directed.nodes.iter() {
+        for node in self.0.nodes.iter() {
             if visited.contains(node) {
                 continue;
             }
@@ -114,7 +112,7 @@ where
     pub fn compact_chains(&mut self) {
         let mut visited = BTreeSet::new();
 
-        let nodes = self.directed.nodes.clone();
+        let nodes = self.0.nodes.clone();
 
         let pb = ProgressBar::new(nodes.len() as u64);
 
@@ -180,7 +178,7 @@ where
 
         println!("Compacted {} nodes", compacted_count);
 
-        self.directed.gc();
+        self.0.gc();
 
         pb.finish();
     }
diff --git a/src/main.rs b/src/main.rs
index b3f4a80..460f880 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -115,9 +115,9 @@ fn main() -> std::io::Result<()> {
 
             let dag = graph.dag();
 
-            compute_edge_types(&dag.0);
+            compute_edge_types(&dag);
 
-            let ccs = compute_ccs(&dag.0);
+            let ccs = compute_ccs(&dag);
 
             println!("Picking largest connected component...");
             // pick the largest connected component
@@ -351,12 +351,15 @@ fn compute_orientation_histogram(graph: &impl Graph<(String, Orientation)>) {
     println!();
 }
 
-fn compute_ccs<V>(graph: &AdjacencyGraph<V>) -> Vec<Vec<V>>
+fn compute_ccs<V>(graph: &impl Graph<V>) -> Vec<Vec<V>>
 where
     V: Ord + Eq + Clone + Debug,
 {
     println!("Computing connected components...");
-    let ccs = graph.undirected().connected_components();
+    let ccs = graph
+        .to_adjecency_graph()
+        .undirected()
+        .connected_components();
 
     println!("Computing sizes histogram...");
     let hist: BTreeMap<_, _> = ccs