d7p2

day7/src/main.rs

@@ -3,6 +3,8 @@ use std::fs::File;
 use std::io::{self, BufRead};
 use std::collections::HashMap;
 
+const MAX_SIZE: usize = 70_000_000 - 30_000_000;
+
 fn main() {
     let file = File::open(&env::args().nth(1).unwrap()).unwrap();
     let mut lines = io::BufReader::new(file).lines();
@@ -37,11 +39,12 @@ fn main() {
         }
     }
 
-    let sum: usize = (0..tree.inodes.len())
+    let total_size = tree.size_of(0);
+    let answer: usize = (0..tree.inodes.len())
         .map(|inode| tree.size_of(inode))
-        .filter(|size| *size <= 100000)
-        .sum();
-    println!("{:?}", sum);
+        .filter(|size| total_size - *size <= MAX_SIZE)
+        .min().unwrap();
+    println!("{:?}", answer);
 }
 
 #[derive(Debug)]

day7/src/main1.rs

@@ -0,0 +1,91 @@
+use std::env;
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::collections::HashMap;
+
+fn main() {
+    let file = File::open(&env::args().nth(1).unwrap()).unwrap();
+    let mut lines = io::BufReader::new(file).lines();
+    let mut tree = DirTree::new();
+    let mut cwd = 0;
+
+    loop {
+        let tokens: Vec<_> = if let Some(Ok(l)) = lines.next() {
+           l.split_whitespace().map(String::from).collect()
+        } else { break; };
+
+        if tokens[0] == "$" {
+            if tokens[1] == "cd" {
+                if tokens[2] == ".." {
+                    cwd = tree.inodes[cwd].parent.unwrap();
+                } else if tokens[2] == "/" {
+                    cwd = 0;
+                } else {
+                    let subdir = tree.inodes[cwd].subdirs[&tokens[2]];
+                    cwd = subdir;
+                }
+            } else if tokens[1] == "ls" {
+                continue;
+            }
+        } else if tokens[0] == "dir" {
+            tree.add_subdir_to(cwd, tokens[1].clone());
+        } else {
+            tree.add_file_to(
+                cwd,
+                tokens[1].clone(),
+                tokens[0].parse::<usize>().unwrap());
+        }
+    }
+
+    let sum: usize = (0..tree.inodes.len())
+        .map(|inode| tree.size_of(inode))
+        .filter(|size| *size <= 100000)
+        .sum();
+    println!("{:?}", sum);
+}
+
+#[derive(Debug)]
+struct Dir {
+    pub files: HashMap<String, usize>, // file name and size
+    pub subdirs: HashMap<String, usize>, // dir name and index into arena
+    pub parent: Option<usize>, // index into arena
+}
+
+#[derive(Debug)]
+struct DirTree {
+    inodes: Vec<Dir>,
+}
+
+impl DirTree {
+    fn new() -> Self {
+        let newdir = Dir {
+            files: HashMap::new(),
+            subdirs: HashMap::new(),
+            parent: None,
+        };
+        DirTree { inodes: vec![newdir] }
+    }
+
+    fn add_subdir_to(&mut self, idx: usize, name: String) {
+        let newidx = self.inodes.len();
+        let newdir = Dir {
+            files: HashMap::new(),
+            subdirs: HashMap::new(),
+            parent: Some(idx),
+        };
+        self.inodes.push(newdir);
+        self.inodes[idx].subdirs.insert(name, newidx);
+    }
+
+    fn add_file_to(&mut self, idx: usize, name: String, size: usize) {
+        self.inodes[idx].files.insert(name, size);
+    }
+
+    fn size_of(&self, inode: usize) -> usize {
+        let size_files: usize = self.inodes[inode].files.values().sum();
+        let size_dirs: usize = self.inodes[inode].subdirs.values()
+            .fold(0, |acc, subdir_inode| acc + self.size_of(*subdir_inode));
+        size_files + size_dirs
+    }
+}
+