2022 day7/rust: add solution

2022/day7/rust/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "rust_2022_07"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+aoc = { path = "../../../common/rust" }

2022/day7/rust/src/main.rs

@@ -0,0 +1,76 @@
+#![warn(clippy::pedantic)]
+
+use std::{
+    collections::HashMap,
+    hash::Hash,
+    io::{stdin, Read},
+    path::{Path, PathBuf},
+};
+
+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 data.lines() {
+        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;
+            }
+        }
+    }
+
+    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_recursive
+            .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);
+}

Cargo.lock

@@ -510,6 +510,13 @@ dependencies = [
  "aoc",
 ]
 
+[[package]]
+name = "rust_2022_07"
+version = "0.1.0"
+dependencies = [
+ "aoc",
+]
+
 [[package]]
 name = "ryu"
 version = "1.0.11"

Cargo.toml

@@ -16,4 +16,5 @@ members = [
 	"2022/day4/rust",
 	"2022/day5/rust",
 	"2022/day6/rust",
+	"2022/day7/rust",
 ]