2022/day7/rust/src/main.rs

@@ -1,62 +1,76 @@
 #![warn(clippy::pedantic)]
 
-use std::{collections::HashMap, io::stdin, path::PathBuf};
+use std::{
+    collections::HashMap,
+    hash::Hash,
+    io::{stdin, Read},
+    path::{Path, PathBuf},
+};
 
-use aoc::PathExt;
-
-fn find_dir_to_delete(dirs: &HashMap<PathBuf, usize>) -> usize {
-    const TOTAL_SPACE: usize = 70_000_000;
-    const REQUIRED_SPACE: usize = 30_000_000;
-
-    let unused = TOTAL_SPACE - dirs[&*PathBuf::from("/")];
-    let to_free = REQUIRED_SPACE - unused;
-
-    let mut sizes: Vec<_> = dirs.values().copied().collect();
-    sizes.sort_unstable();
-    match sizes.binary_search(&to_free) {
-        Ok(i) | Err(i) => sizes[i],
-    }
-}
+use aoc::*;
 
 fn main() {
+    let mut data = String::new();
+    stdin().read_to_string(&mut data).unwrap();
+
     let mut cwd = PathBuf::new();
     cwd.push("/");
     let mut dirs: HashMap<PathBuf, usize> = HashMap::new();
 
-    for line in stdin().lines() {
-        let line = line.unwrap();
-
+    for line in data.lines() {
         if let Some(command) = line.strip_prefix("$ ") {
             let mut args = command.split_whitespace();
-
-            if args.next().unwrap() != "cd" {
-                continue;
+            let command = args.next().unwrap();
+            match command {
+                "ls" => {
+                    dirs.remove(&cwd);
                 }
-
-            match args.next().unwrap() {
+                "cd" => {
+                    let dir = args.next().unwrap();
+                    match dir {
                         ".." => assert!(cwd.pop()),
-                path => {
-                    cwd.push(path);
-                    assert!(!dirs.contains_key(&cwd));
+                        path => cwd.push(path),
                     }
                 }
+                _ => panic!("unknown command {command}"),
+            }
         } else {
-            let size = line.split_whitespace().next().unwrap();
+            let (size, _name) = line.split_once(' ').unwrap();
             if size == "dir" {
-                continue;
+                // skip
+            } else {
+                let size: usize = size.parse().unwrap();
+                *dirs.entry(cwd.clone()).or_default() += size;
+            }
+        }
     }
 
-            let size: usize = size.parse().unwrap();
-            for dir in cwd.parents() {
-                *dirs.entry(dir.to_path_buf()).or_default() += size;
-            }
+    let mut dirs_recursive: HashMap<&Path, usize> = HashMap::new();
+    for (dir, size) in &dirs {
+        for parent in std::iter::successors(Some(&**dir), |dir| dir.parent()) {
+            *dirs_recursive.entry(parent).or_default() += size;
         }
     }
 
     println!(
         "{}",
-        dirs.values().filter(|&&s| s <= 100_000).sum::<usize>()
+        dirs_recursive
+            .values()
+            .filter(|&&s| s <= 100_000)
+            .sum::<usize>()
     );
 
-    println!("{}", find_dir_to_delete(&dirs));
+    const TOTAL_SPACE: usize = 70_000_000;
+    const REQUIRED_SPACE: usize = 30_000_000;
+
+    let unused = TOTAL_SPACE - dirs_recursive[&*PathBuf::from("/")];
+    let to_free = REQUIRED_SPACE - unused;
+    let mut sizes: Vec<_> = dirs_recursive.values().copied().collect();
+    sizes.sort_unstable();
+    let size = match sizes.binary_search(&to_free) {
+        Ok(i) => sizes[i],
+        Err(larger) => sizes[larger],
+    };
+
+    println!("{}", size);
 }

common/rust/src/lib.rs

@@ -2,7 +2,7 @@
 
 mod section_range;
 
-use std::{mem, path::Path};
+use std::mem;
 
 pub use section_range::{EmptyRange, InvalidSectionString, SectionRange};
 
@@ -61,18 +61,3 @@ impl<T> Iterator for UpToTwoIter<T> {
         ret
     }
 }
-
-pub trait PathExt {
-    type Iter<'a>: Iterator<Item = &'a Path>
-    where
-        Self: 'a;
-    fn parents(&self) -> Self::Iter<'_>;
-}
-
-impl PathExt for Path {
-    type Iter<'a> = std::iter::Successors<&'a Path, for<'p> fn(&&'p Path) -> Option<&'p Path>>;
-
-    fn parents(&self) -> Self::Iter<'_> {
-        std::iter::successors(Some(self), |dir| dir.parent())
-    }
-}