Solution for 2022/day07-part1

2022/day07-part1/src/main.rs

@@ -1,7 +1,7 @@
-use std::{cell::RefCell, rc::Rc};
+use std::{cell::RefCell, fmt, rc::Rc};
 
 // Custom data structure
-#[derive(Copy, Clone, Debug)]
+#[derive(Eq, PartialEq, Copy, Clone, Debug)]
 enum NodeType {
     File,
     Directory,
@@ -9,11 +9,27 @@ enum NodeType {
 
 use NodeType::*;
 
+// #[derive(Debug)]
 struct Node {
     node_type: NodeType,
     name: String,
     size: usize,
     children: Vec<Rc<RefCell<Node>>>,
+    parent: Option<Rc<RefCell<Node>>>,
+}
+
+// Manual implementation of Debug for Node.
+// Necessary in order to remove the "parent" field from the output.
+// Otherwise the printer will print indefinitely.
+impl fmt::Debug for Node {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Node")
+            .field("node_type", &self.node_type)
+            .field("name", &self.name)
+            .field("size", &self.size)
+            .field("children", &self.children)
+            .finish()
+    }
 }
 
 impl Node {
@@ -23,6 +39,7 @@ impl Node {
             name: String::from(name),
             size,
             children: Vec::new(),
+            parent: None,
         }))
     }
 }
@@ -40,13 +57,20 @@ fn main() {
     let input = input.lines();
 
     // --- TASK BEGIN ---
-    let mut result = 0;
 
     // Set up our filesystem, starting with the root directory as the root node.
     let root = Node::new(Directory, "/", 0);
 
-    // Also set up a
+    // Also keep track of all directories in the graph separately.
-    let current = root;
+    // This will help us actually determine the sum we're supposed to look for.
+    let mut dir_list: Vec<Rc<RefCell<Node>>> = Vec::new();
+    dir_list.push(root.clone());
+
+    // Also set up a pointer for the current directory.
+    let mut cd = root.clone();
+
+    // Keep track whether we're currently reading directories.
+    let mut ls_mode = false;
 
     // Read line by line
     for line in input {
@@ -55,11 +79,111 @@ fn main() {
 
         // First of all, differentiate between command and list item.
         if line[0] == "$" {
-
+            match line[1] {
+                "cd" => {
+                    // Changing directory.
+                    ls_mode = false;
+                    match line[2] {
+                        "/" => {
+                            // If the target is "/" switch back to the root directory.
+                            cd = root.clone();
+                        }
+                        ".." => {
+                            // Switch to parent directory.
+                            // First, we need to borrow the actual Node of the current directory.
+                            let cd_node = cd.borrow();
+                            // Grab an Rc to the parent...
+                            let pd = cd_node.parent.clone().unwrap();
+                            drop(cd_node);
+                            // ...and assign it to cd.
+                            cd = pd;
+                        }
+                        dir => {
+                            // In the standard case, look for the child-node with the correct name.
+                            // Get from the Rc<RefCell<Node>> to the actual Node.
+                            let cd_node = cd.borrow();
+                            // From there, find the child directory with the matching name.
+                            let target_dir = cd_node
+                                .children
+                                .iter()
+                                .find(|x| x.borrow().name == dir)
+                                .unwrap()
+                                .clone();
+                            // Drop the Ref<_, Node> to ensure we drop the borrow on cd.
+                            drop(cd_node);
+                            // Now assign the new "current directory".
+                            cd = target_dir;
+                        }
+                    }
+                }
+                "ls" => {
+                    ls_mode = true;
+                }
+                _ => (),
+            }
         } else {
-            println!("item");
+            // Looks like we're in list mode... right?
+            assert!(ls_mode);
+
+            // Assume it is a directory.
+            let mut node_type = Directory;
+            let mut size: usize = 0;
+            let name = line[1];
+
+            // If it is a file, update the size and type accordingly.
+            if line[0] != "dir" {
+                node_type = File;
+                size = line[0].parse::<usize>().unwrap();
+            }
+
+            // Now create the node for this file / directory.
+            let node = Node::new(node_type, name, size);
+            // Update the children of the current directory.
+            cd.borrow_mut().children.push(node.clone());
+            // And ensure the new node points back to the current directory.
+            node.borrow_mut().parent = Some(cd.clone());
+
+            // Also add any new directories to the directory list.
+            if node_type == Directory {
+                dir_list.push(node.clone());
+            }
         }
     }
 
-    println!("Result: {}", result);
+    // All files and directories have been parsed into the data structure.
+    // However, the size on all directories is currently 0.
+    // Determine the size of all directories recursively using DFS.
+    calc_node_size(root.clone());
+
+    // Finally, actually perform what the task requested.
+    let mut total: usize = 0;
+    for dir in &dir_list {
+        let size = dir.borrow().size;
+        if size <= 100000 {
+            total += size;
+        }
+    }
+
+    println!("Result: {}", total);
+}
+
+// Perform a depth-first-search on the tree in order to annotate the directory sizes.
+// This method uses recursion to visit the entire tree.
+fn calc_node_size(node: Rc<RefCell<Node>>) -> usize {
+    let mut inner_node = node.borrow_mut();
+    // If this node is a file, there's no recursion to be done.
+    // Simply return the size of the file.
+    if inner_node.node_type == File {
+        inner_node.size
+    } else {
+        let mut size: usize = 0;
+        // Iterate through all children and ...
+        for child in &inner_node.children {
+            // ... accumulate the size of all nodes recursively.
+            size += calc_node_size(child.clone());
+        }
+        // One more thing: Update the size of this directory before returning.
+        inner_node.size = size;
+        size
+    }
 }