day 7 part 1 in rust!

07/main.go

@@ -36,7 +36,6 @@ func makeScanner(test bool) *bufio.Scanner {
 
 type Folder struct {
 	name    string
-	parent  *Folder
 	files   map[string]int
 	folders map[string]*Folder
 	size    int
@@ -79,7 +78,6 @@ func partOne() {
 			name := strings.Split(line, " ")[1]
 			stack[len(stack)-1].folders[name] = &Folder{
 				name:    name,
-				parent:  stack[len(stack)-1],
 				files:   map[string]int{},
 				folders: map[string]*Folder{},
 			}
@@ -87,12 +85,16 @@ func partOne() {
 			stack[len(stack)-1].files[strings.Split(line, " ")[1]] = mustAtoi(strings.Split(line, " ")[0])
 		}
 	}
-	// compute root size
-	for _, size := range root.files {
-		root.size += size
-	}
-	for _, f := range root.folders {
-		root.size += f.size
+	// finish computing directory sizes
+	for len(stack) > 0 {
+		curr := stack[len(stack)-1]
+		for _, size := range curr.files {
+			curr.size += size
+		}
+		for _, f := range curr.folders {
+			curr.size += f.size
+		}
+		stack = stack[0 : len(stack)-1]
 	}
 	fmt.Println(sum)
 }
@@ -105,7 +107,7 @@ func partTwo() {
 		files:   map[string]int{},
 		folders: map[string]*Folder{},
 	}
-	spaceToFree := 30000000 - (70000000 - 49192532)
+	spaceToFree := 30000000 - (70000000 - 49192532) // size of all files, precomputed
 	toDelete := 70000000
 	stack := []*Folder{&root}
 	for scanner.Scan() {
@@ -135,7 +137,6 @@ func partTwo() {
 			name := strings.Split(line, " ")[1]
 			stack[len(stack)-1].folders[name] = &Folder{
 				name:    name,
-				parent:  stack[len(stack)-1],
 				files:   map[string]int{},
 				folders: map[string]*Folder{},
 			}
@@ -152,6 +153,9 @@ func partTwo() {
 		for _, f := range curr.folders {
 			curr.size += f.size
 		}
+		if curr.size > spaceToFree && curr.size < toDelete {
+			toDelete = curr.size
+		}
 		stack = stack[0 : len(stack)-1]
 	}
 	fmt.Println(toDelete)

07/main.rs

@@ -7,18 +7,11 @@ use std::path::Path;
 use std::time::Instant;
 
 #[derive(Debug, Clone)]
-struct ElfFile {
-    name: String,
+struct Folder {
+    folders: HashMap<String, u32>,
     size: u32,
 }
 
-#[derive(Debug, Clone)]
-struct Folder<'a> {
-    name: String,
-    files: HashMap<String, ElfFile>,
-    folders: HashMap<String, &'a Folder<'a>>,
-}
-
 fn main() {
     let now = Instant::now();
     part_one();
@@ -41,58 +34,40 @@ where
     Ok(io::BufReader::new(file).lines())
 }
 
-fn ElfFile_FromStr(s: &str) -> ElfFile {
-    let mut f = s.split(" ");
-    return ElfFile {
-        size: f.next().unwrap().parse::<u32>().unwrap(),
-        name: f.next().unwrap().to_string(),
-    };
-}
-
-fn newFolder(s: &str) -> Folder {
-    return Folder {
-        name: s.to_string(),
-        files: HashMap::new(),
-        folders: HashMap::new(),
-    };
-}
-
 fn part_one() {
     if let Ok(lines) = read_lines("./inputs/input") {
-        let mut tree = Folder {
-            name: "/".to_string(),
-            files: HashMap::new(),
-            folders: HashMap::new(),
-        };
-        let mut stack: Vec<&mut Folder> = vec![&mut tree];
+        let mut sum = 0;
+        let mut stack: Vec<u32> = vec![0];
         for line in lines {
             if let Ok(command) = line {
                 match command.as_str() {
-                    "$ cd /" => continue, // skip start
+                    "$ 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 .." => {
-                        // stack.pop();
+                        let f = stack.pop().unwrap();
+                        if f < 100000 {
+                            sum += f
+                        }
+                        let mut p = stack.pop().unwrap();
+                        p += f;
+                        stack.push(p);
                     }
                     s if s.starts_with("$ cd ") => {
-                        println!("push {}\n", s.split(" ").nth(2).unwrap())
-                    }
-                    s if s.starts_with("dir ") => {
-                        let f = stack.pop().unwrap();
-                        let ef = newFolder(s.split(" ").nth(1).unwrap());
-                        f.folders.insert(ef.name.clone(), &ef);
-                        stack.push(f);
+                        stack.push(0);
                     }
                     s => {
                         // otherwise it must be a file
-                        let f = stack.pop().unwrap();
-                        let ef = ElfFile_FromStr(s);
-                        f.files.insert(ef.name.clone(), ef);
+                        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!("{:?}", tree);
+        println!("{:?}", sum);
     }
 }