finish Day 7 pt2

src/bin/07.rs

@@ -1,6 +1,11 @@
 use std::{cell::RefCell, collections::HashMap, rc::Rc};
 
+// note: had first created file struct and only during get_total would add to size of struct
+//       but was extra overhead not necessary for solving problem. Might reintroduce for cleanliness later
+
 const DIRECTORY_CAPACITY: usize = 100000;
+const TOTAL_SPACE: usize = 70000000;
+const REQUIRED_SPACE: usize = 30000000;
 
 struct BaseDirectory {
     root: Rc<Directory>,
@@ -17,7 +22,7 @@ impl BaseDirectory {
             }),
         };
     }
-    pub fn parse_part_one(&self, input: &str) {
+    pub fn parse_input(&self, input: &str) {
         let mut current_directory = self.root.clone();
         for line in input.lines().skip(1) {
             let args = line.split(" ").collect::<Vec<&str>>();
@@ -61,19 +66,18 @@ struct Directory {
 }
 impl Directory {
     pub fn get_total(&self) -> usize {
-        let mut total = *self.size.borrow();
-        total += self
-            .subdirs
-            .borrow()
-            .values()
-            .fold(0, |acc, subdir| acc + subdir.get_total());
-        return total;
+        return *self.size.borrow()
+            + self
+                .subdirs
+                .borrow()
+                .values()
+                .fold(0, |acc, subdir| acc + subdir.get_total());
     }
 }
 
 pub fn part_one(input: &str) -> Option<u32> {
     let base_directory = BaseDirectory::new();
-    base_directory.parse_part_one(input);
+    base_directory.parse_input(input);
     let mut directories = vec![Rc::clone(&base_directory.root)];
     let mut total = 0;
     while let Some(dir) = directories.pop() {
@@ -85,11 +89,31 @@ pub fn part_one(input: &str) -> Option<u32> {
             total += size;
         }
     }
-    println!("total: {}", total);
     return Some(total as u32);
 }
+
+pub fn smallest_dir_required(total: usize) -> usize {
+    let free_space = TOTAL_SPACE - total;
+    return REQUIRED_SPACE - free_space;
+}
 pub fn part_two(input: &str) -> Option<u32> {
-    None
+    let base_directory = BaseDirectory::new();
+    base_directory.parse_input(input);
+    let required_space = smallest_dir_required(base_directory.root.get_total());
+
+    let mut directories = vec![Rc::clone(&base_directory.root)];
+
+    let mut smallest_required = usize::MAX;
+    while let Some(dir) = directories.pop() {
+        for subdir in dir.subdirs.borrow().values() {
+            directories.push(subdir.clone());
+        }
+        let size = dir.get_total();
+        if size >= required_space {
+            smallest_required = smallest_required.min(size);
+        }
+    }
+    return Some(smallest_required as u32);
 }
 
 fn main() {
@@ -106,11 +130,13 @@ mod tests {
     fn test_part_one() {
         let input = advent_of_code::read_file("examples", 7);
         println!("{:?}", part_one(&input));
+        assert_eq!(part_one(&input), Some(95437));
     }
 
     #[test]
     fn test_part_two() {
         let input = advent_of_code::read_file("examples", 7);
-        assert_eq!(part_two(&input), None);
+        println!("{:?}", part_two(&input));
+        assert_eq!(part_two(&input), Some(24933642));
     }
 }