day 9

README.md

@@ -32,6 +32,7 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 6](./src/bin/06.rs) | `358.0µs` | `31.5ms` |
 | [Day 7](./src/bin/07.rs) | `487.3µs` | `862.0µs` |
 | [Day 8](./src/bin/08.rs) | `36.5µs` | `116.8µs` |
+| [Day 9](./src/bin/09.rs) | `78.7µs` | `-` |
 
-**Total: 35.37ms**
+**Total: 35.45ms**
 <!--- benchmarking table --->

data/examples/09.txt

@@ -0,0 +1 @@
+2333133121414131402

src/bin/09.rs

@@ -0,0 +1,110 @@
+use std::collections::VecDeque;
+
+advent_of_code::solution!(9);
+
+#[derive(Debug, Eq, Hash, PartialEq, Clone, Copy)]
+enum Block {
+    File(u32),
+    Free(u32),
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let mut queue: VecDeque<Block> =
+        VecDeque::from_iter(input.chars().enumerate().filter_map(|(idx, ch)| {
+            if let Some(value) = ch.to_digit(10) {
+                if idx % 2 == 0 {
+                    Some(Block::File(value))
+                } else {
+                    Some(Block::Free(value))
+                }
+            } else {
+                None
+            }
+        }));
+    let mut curr_lower_file_id: u64 = 0;
+    let mut curr_upper_file_id: u64 = (queue.len() - 2).div_ceil(2) as u64;
+    let mut curr_idx = 0;
+
+    let mut result: u64 = 0;
+    while !queue.is_empty() {
+        let Some(front_candidate) = queue.pop_front() else {
+            break;
+        };
+        match front_candidate {
+            Block::File(size) => {
+                for offset in 0..size {
+                    result += curr_lower_file_id * (curr_idx + offset) as u64;
+                }
+                curr_idx += size;
+                curr_lower_file_id += 1;
+            }
+            Block::Free(size) => {
+                let r_size = if let Some(r) = queue.pop_back() {
+                    match r {
+                        Block::File(r_size) => r_size,
+                        Block::Free(_) => {
+                            if let Some(r2) = queue.pop_back() {
+                                match r2 {
+                                    Block::File(r2_size) => r2_size,
+                                    Block::Free(_) => panic!("Double free lol"),
+                                }
+                            } else {
+                                break;
+                            }
+                        }
+                    }
+                } else {
+                    break;
+                };
+
+                match size.cmp(&r_size) {
+                    std::cmp::Ordering::Less => {
+                        for offset in 0..size {
+                            result += curr_upper_file_id * (curr_idx + offset) as u64;
+                        }
+                        queue.push_back(Block::File(r_size - size));
+                        curr_idx += size;
+                    }
+                    std::cmp::Ordering::Equal => {
+                        for offset in 0..size {
+                            result += curr_upper_file_id * (curr_idx + offset) as u64;
+                        }
+                        curr_upper_file_id -= 1;
+                        curr_idx += size;
+                    }
+                    std::cmp::Ordering::Greater => {
+                        for offset in 0..r_size {
+                            result += curr_upper_file_id * (curr_idx + offset) as u64;
+                        }
+                        queue.push_front(Block::Free(size - r_size));
+                        curr_upper_file_id -= 1;
+                        curr_idx += r_size;
+                    }
+                }
+            }
+        }
+    }
+
+    Some(result)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(1928));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}