2022 day7/rust: cleanup

2022/day7/rust/src/main.rs

@@ -1,76 +1,62 @@
 #![warn(clippy::pedantic)]
 
-use std::{
-    collections::HashMap,
-    hash::Hash,
-    io::{stdin, Read},
-    path::{Path, PathBuf},
-};
+use std::{collections::HashMap, io::stdin, path::PathBuf};
 
-use aoc::*;
+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],
+    }
+}
 
 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 data.lines() {
+    for line in stdin().lines() {
+        let line = line.unwrap();
+
         if let Some(command) = line.strip_prefix("$ ") {
             let mut args = command.split_whitespace();
-            let command = args.next().unwrap();
-            match command {
-                "ls" => {
-                    dirs.remove(&cwd);
-                }
-                "cd" => {
-                    let dir = args.next().unwrap();
-                    match dir {
-                        ".." => assert!(cwd.pop()),
-                        path => cwd.push(path),
-                    }
-                }
-                _ => panic!("unknown command {command}"),
-            }
-        } else {
-            let (size, _name) = line.split_once(' ').unwrap();
-            if size == "dir" {
-                // skip
-            } else {
-                let size: usize = size.parse().unwrap();
-                *dirs.entry(cwd.clone()).or_default() += size;
-            }
-        }
+
+            if args.next().unwrap() != "cd" {
+                continue;
             }
 
-    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;
+            match args.next().unwrap() {
+                ".." => assert!(cwd.pop()),
+                path => {
+                    cwd.push(path);
+                    assert!(!dirs.contains_key(&cwd));
+                }
+            }
+        } else {
+            let size = line.split_whitespace().next().unwrap();
+            if size == "dir" {
+                continue;
+            }
+
+            let size: usize = size.parse().unwrap();
+            for dir in cwd.parents() {
+                *dirs.entry(dir.to_path_buf()).or_default() += size;
+            }
         }
     }
 
     println!(
         "{}",
-        dirs_recursive
-            .values()
-            .filter(|&&s| s <= 100_000)
-            .sum::<usize>()
+        dirs.values().filter(|&&s| s <= 100_000).sum::<usize>()
     );
 
-    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);
+    println!("{}", find_dir_to_delete(&dirs));
 }