pub use std::collections::{HashSet, HashMap};
use graph::{Graph, Ungraph, Digraph};

mod graph;
mod traversal;
mod tree;

fn main() {
    let mut g = Ungraph::new();

    println!("{}", g);
    g.add_node('a');
    g.add_node('b');
    g.add_node('c');
    println!("{}", g);
    g.add_edge(0, 1);
    g.add_edge(0, 2);
    println!("{}", g);


    let mut h = Digraph::new();

    println!("{}", h);
    h.add_node('a');
    h.add_node('b');
    h.add_node('c');
    println!("{}", h);
    h.add_edge(0, 1);
    h.add_edge(0, 2);
    println!("{}", h);
}

pub use std::collections::{HashSet, HashMap};

mod graph;
mod traversal;
mod tree;

fn main() {

}

--- 
+++ 
@@ -1,9 +1,31 @@
 pub use std::collections::{HashSet, HashMap};
+use graph::{Graph, Ungraph, Digraph};
 
 mod graph;
 mod traversal;
 mod tree;
 
 fn main() {
+    let mut g = Ungraph::new();
 
+    println!("{}", g);
+    g.add_node('a');
+    g.add_node('b');
+    g.add_node('c');
+    println!("{}", g);
+    g.add_edge(0, 1);
+    g.add_edge(0, 2);
+    println!("{}", g);
+
+
+    let mut h = Digraph::new();
+
+    println!("{}", h);
+    h.add_node('a');
+    h.add_node('b');
+    h.add_node('c');
+    println!("{}", h);
+    h.add_edge(0, 1);
+    h.add_edge(0, 2);
+    println!("{}", h);
 }
Add some basic tests in main
