default source distance infinity

src/main.rs

@@ -9,6 +9,7 @@ use std::{
     cell::RefCell,
     collections::{hash_map::Entry, HashMap},
     env,
+    f64::INFINITY,
     rc::Rc,
 };
 
@@ -30,7 +31,7 @@ impl Node {
         Node {
             destinations,
             origin,
-            source_distance: 0.0,
+            source_distance: INFINITY,
             visited: false,
         }
     }