and part 2

07/main.rs

@@ -1,17 +1,10 @@
 #![allow(dead_code)]
-use std::collections::HashMap;
 use std::fs::File;
 use std::io;
 use std::io::BufRead;
 use std::path::Path;
 use std::time::Instant;
 
-#[derive(Debug, Clone)]
-struct Folder {
-    folders: HashMap<String, u32>,
-    size: u32,
-}
-
 fn main() {
     let now = Instant::now();
     part_one();
@@ -71,4 +64,40 @@ fn part_one() {
     }
 }
 
-fn part_two() {}
+fn part_two() {
+    if let Ok(lines) = read_lines("./inputs/input") {
+        let mut stack: Vec<u32> = vec![0];
+        let space_to_free = 30000000 - (70000000 - 49192532); // size of all files, precomputed
+        let mut to_delete = 70000000;
+        for line in lines {
+            if let Ok(command) = line {
+                match command.as_str() {
+                    "$ cd /" => continue,                   // skip start
+                    "$ ls" => continue, // we can assume this if we're not moving between directories
+                    s if s.starts_with("dir ") => continue, // we'll get there when we `cd`
+                    "$ cd .." => {
+                        let f = stack.pop().unwrap();
+                        if f > space_to_free && f < to_delete {
+                            to_delete = f
+                        }
+                        let mut p = stack.pop().unwrap();
+                        p += f;
+                        stack.push(p);
+                    }
+                    s if s.starts_with("$ cd ") => {
+                        stack.push(0);
+                    }
+                    s => {
+                        // otherwise it must be a file
+                        let mut f = stack.pop().unwrap();
+                        let mut sp = s.split(" ");
+                        let size = sp.next().unwrap().parse::<u32>().unwrap();
+                        f += size;
+                        stack.push(f);
+                    }
+                };
+            }
+        }
+        println!("{:?}", to_delete);
+    }
+}