Clean up handling of root node

src/day07.rs

@@ -23,14 +23,6 @@ impl DirectoryEntry {
             None
         }
     }
-
-    fn as_dir(&self) -> Option<&String> {
-        if let Self::Dir(v) = self {
-            Some(v)
-        } else {
-            None
-        }
-    }
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -58,16 +50,6 @@ enum CliOperation {
     Ls(Vec<DirectoryEntry>),
 }
 
-impl CliOperation {
-    fn as_ls(&self) -> Option<&Vec<DirectoryEntry>> {
-        if let Self::Ls(v) = self {
-            Some(v)
-        } else {
-            None
-        }
-    }
-}
-
 #[aoc_generator(day7)]
 fn input_generator(input: &str) -> Vec<CliOperation> {
     let mut lines = input.lines().peekable();
@@ -95,19 +77,7 @@ fn compute_dir_sizes(input: &[CliOperation]) -> Tree<(usize, usize)> {
     }
     let mut tree = Tree::new();
     let mut current_node = tree
-        .insert(
+        .insert(Node::new((0, 0)), InsertBehavior::AsRoot)
-            Node::new((
-                input[1]
-                    .as_ls()
-                    .unwrap()
-                    .iter()
-                    .filter_map(DirectoryEntry::as_file)
-                    .map(|file| file.size)
-                    .sum::<usize>(),
-                0,
-            )),
-            InsertBehavior::AsRoot,
-        )
         .unwrap();
     for op in input {
         match op {