Solution for 2022/day07-part2

2022/day07-part2/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day07-part2"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2022/day07-part2/src/main.rs

@@ -0,0 +1,204 @@
+use std::{cell::RefCell, fmt, rc::Rc};
+
+// Custom data structure
+#[derive(Eq, PartialEq, Copy, Clone, Debug)]
+enum NodeType {
+    File,
+    Directory,
+}
+
+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 {
+    fn new(node_type: NodeType, name: &str, size: usize) -> Rc<RefCell<Node>> {
+        Rc::new(RefCell::new(Node {
+            node_type,
+            name: String::from(name),
+            size,
+            children: Vec::new(),
+            parent: None,
+        }))
+    }
+}
+
+fn main() {
+    // Use command line arguments to specify the input filename.
+    let args: Vec<String> = std::env::args().collect();
+    if args.len() < 2 {
+        panic!("Usage: ./main <input-file>\nNo input file provided. Exiting.");
+    }
+
+    // Next, read the contents of the input file into a string for easier processing.
+    let input = std::fs::read_to_string(&args[1]).expect("Error opening file");
+    // Line-by-line processing is easiest.
+    let input = input.lines();
+
+    // --- TASK BEGIN ---
+
+    // Set up our filesystem, starting with the root directory as the root node.
+    let root = Node::new(Directory, "/", 0);
+
+    // Also keep track of all directories in the graph separately.
+    // 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 {
+        // Split any incoming line by spaces, makes our life easier down the line.
+        let line = line.split(' ').collect::<Vec<_>>();
+
+        // 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 {
+            // 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());
+            }
+        }
+    }
+
+    // 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. (part one)
+    // let mut total: usize = 0;
+    // for dir in &dir_list {
+    //     let size = dir.borrow().size;
+    //     if size <= 100000 {
+    //         total += size;
+    //     }
+    // }
+
+    // Determine the amount of space we need to free.
+    let to_free: usize = root.borrow().size - 40000000;
+    let mut optimal_dir_size: usize = 70000000;
+    for dir in &dir_list {
+        let size = dir.borrow().size;
+        // Dont' bother if the directory is too small.
+        if size < to_free {
+            continue;
+        } else {
+            // Looks like it's big enough.
+            // Update our optimal result if it is the smalles we've encountered yet.
+            optimal_dir_size = std::cmp::min(size, optimal_dir_size);
+        }
+    }
+
+    println!("Result: {}", optimal_dir_size);
+}
+
+// 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
+    }
+}