Continued

src/lib.rs

@@ -5,6 +5,7 @@ struct Node {
     left: Option<Box<Self>>,
     right: Option<Box<Self>>,
     character: Option<char>,
+    frequency: i32,
 }
 
 impl Node {
@@ -13,22 +14,26 @@ impl Node {
             left: None,
             right: None,
             character: None,
+            frequency: 0,
         }
     }
 
-    pub fn new_with_character(character: char) -> Node {
+    pub fn new_with_character(character: char, frequency: i32) -> Node {
         Self {
             character: Some(character),
             left: None,
             right: None,
+            frequency
         }
     }
 
     pub fn join_left(self: &mut Node, left: Box<Node>) {
+        self.frequency += left.get_frequency();
         self.left = Some(left);
     }
 
     pub fn join_right(self: &mut Node, right: Box<Node>) {
+        self.frequency += right.get_frequency();
         self.right = Some(right);
     }
 
@@ -36,6 +41,10 @@ impl Node {
         self.left.is_none() & self.right.is_none()
     }
 
+    pub fn get_frequency(self: &Node) -> i32 {
+        self.frequency
+    }
+
     pub fn get_character(self: &Node) -> Result<char, &str> {
         if !self.is_leaf() {
             return Err("This node is not a leaf node.");
@@ -44,3 +53,31 @@ impl Node {
         Ok(self.character.unwrap())
     }
 }
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn make_new_node_with_character_works() {
+        use crate::Node;
+
+        let example = Node::new_with_character('a', 5);
+        assert!(example.is_leaf());
+        assert_eq!(example.get_character().unwrap(), 'a');
+    }
+
+    #[test]
+    fn make_small_tree_with_leaf_nodes() {
+        use crate::Node;
+
+        let mut root = Node::new();
+        let left = Node::new_with_character('a', 5);
+        let right = Node::new_with_character('b', 10);
+
+
+        root.join_left(Box::new(left));
+        root.join_right(Box::new(right));
+
+        assert!(!root.is_leaf());
+        assert_eq!(root.get_frequency(), 15);
+    }
+}