aoc/src/aoc2022/day07/mod.rs

use std::{
    cell::RefCell,
    rc::{Rc, Weak},
};

#[derive(Debug)]
enum NodeType {
    File(usize),
    Dir(RefCell<Vec<Rc<Node>>>),
}

#[derive(Debug)]
struct Node {
    name: String,
    typ: NodeType,
    parent: Weak<Node>,
}

impl Node {
    fn get_size(&self) -> usize {
        let mut size = 0;

        match &self.typ {
            NodeType::File(filesize) => size = *filesize,
            NodeType::Dir(dir_nodes) => {
                for node in dir_nodes.borrow().iter() {
                    size += node.get_size()
                }
            }
        }

        size
    }
}

fn parse_input(input: &str) -> Rc<Node> {
    let root_node: Rc<Node> = Rc::new(Node {
        name: String::from("/"),
        typ: NodeType::Dir(RefCell::new(Vec::new())),
        parent: Weak::new(),
    });

    let mut current_dir: Rc<Node> = root_node.clone();

    for line in input.lines() {
        if line.is_empty() {
            continue;
        }

        let mut split = line.split_whitespace();
        let first = split.next().unwrap();
        let second = split.next().unwrap();

        match (first, second) {
            ("$", "cd") => {
                let next = split.next().unwrap();
                if next != "/" {
                    match next {
                        ".." => {
                            let bla = current_dir.parent.upgrade().unwrap();
                            current_dir = bla;
                        }
                        dir => {
                            let mut new_dir = current_dir.clone();
                            if let NodeType::Dir(nodes) = &current_dir.typ {
                                new_dir = nodes
                                    .borrow()
                                    .iter()
                                    .find(|n| n.name == dir)
                                    .unwrap()
                                    .clone();
                            }
                            current_dir = new_dir;
                        }
                    }
                }
            }
            ("$", "ls") => (),
            (typ_size, name) => {
                if let Ok(size) = typ_size.parse::<usize>() {
                    let new_node = Node {
                        name: name.to_string(),
                        typ: NodeType::File(size),
                        parent: Rc::downgrade(&current_dir),
                    };

                    if let NodeType::Dir(nodes) = &current_dir.typ {
                        nodes.borrow_mut().push(Rc::new(new_node));
                    }
                } else {
                    let new_node = Node {
                        name: name.to_string(),
                        typ: NodeType::Dir(RefCell::new(Vec::new())),
                        parent: Rc::downgrade(&current_dir),
                    };

                    if let NodeType::Dir(nodes) = &current_dir.typ {
                        nodes.borrow_mut().push(Rc::new(new_node));
                    }
                }
            }
        }
    }

    root_node
}

fn find(node: Rc<Node>, max_size: usize) -> usize {
    let mut total_size = 0;

    if let NodeType::Dir(nodes) = &node.typ {
        for node in nodes.borrow().iter() {
            if let NodeType::Dir(_) = &node.typ {
                let size = node.get_size();
                if size < max_size {
                    total_size += size;
                }
                total_size += find(node.clone(), max_size);
            }
        }
    }

    total_size
}

fn find_best_fit(node: Rc<Node>, size: usize) -> usize {
    let mut actual_size = usize::MAX;

    if let NodeType::Dir(nodes) = &node.typ {
        for node in nodes.borrow().iter() {
            if let NodeType::Dir(_) = &node.typ {
                let node_size = node.get_size();
                if node_size >= size {
                    if actual_size > node_size {
                        actual_size = node_size;
                    }
                    let deeper = find_best_fit(node.clone(), size);

                    if actual_size > deeper {
                        actual_size = deeper;
                    }
                }
            }
        }
    }

    actual_size
}

pub fn task_one(input: &str) -> String {
    let root = parse_input(&input);

    // if let NodeType::Dir(nodes) = &root.typ {
    //     println!("{:?}", nodes.borrow())
    // }

    find(root, 100_000).to_string()
}

pub fn task_two(input: &str) -> String {
    const TOTAL_SPACE: usize = 70_000_000;
    const REQUIRED_FREE_SPACE: usize = 30_000_000;

    let root = parse_input(&input);
    let required_space = REQUIRED_FREE_SPACE - (TOTAL_SPACE - root.get_size());

    find_best_fit(root, required_space).to_string()
}