day 9 part 1

src/day09.rs

@@ -0,0 +1,74 @@
+use std::fs::read_to_string;
+
+pub fn day_main() {
+    let input = read_to_string("input/day09.txt").unwrap();
+    let input = input.trim();
+    println!(" part1: {}", part1(input));
+    println!(" part2: {}", part2(input));
+}
+
+type RiddleResult = usize;
+
+fn part1(input: &str) -> RiddleResult {
+    let mut disk = Vec::with_capacity(input.len() * 10);
+    for (i, l) in input.chars().enumerate() {
+        let l = l.to_digit(10).unwrap();
+        let content = if i % 2 == 0 {
+            // file
+            Some(i / 2) // id based on order of apperance and every second one is a file
+        } else {
+            None
+        };
+        for j in 0..l {
+            disk.push(content);
+        }
+    }
+    // dbg!(disk);
+    let mut free = disk
+        .iter()
+        .enumerate()
+        .find(|(_, v)| v.is_none())
+        .unwrap()
+        .0;
+    let mut last_block = disk.len() - 1;
+
+    while free < last_block {
+        if disk[free].is_some() {
+            break;
+        }
+        disk[free] = disk[last_block];
+        disk[last_block] = None;
+        while last_block > 0 && disk[last_block].is_none() {
+            last_block -= 1;
+        }
+        while free < disk.len() && disk[free].is_some() {
+            free += 1;
+        }
+    }
+    disk.into_iter()
+        .take(free)
+        .enumerate()
+        .map(|(i, v)| i * v.unwrap())
+        .sum()
+}
+
+fn part2(_input: &str) -> RiddleResult {
+    0
+}
+
+#[cfg(test)]
+mod test {
+    use super::{part1, part2};
+
+    const TEST_INPUT: &str = r"2333133121414131402";
+
+    #[test]
+    fn test1() {
+        assert_eq!(part1(TEST_INPUT), 1928);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(part2(TEST_INPUT), 0);
+    }
+}

src/lib.rs

@@ -6,4 +6,5 @@ pub mod day05;
 pub mod day06;
 pub mod day07;
 pub mod day08;
+pub mod day09;
 pub mod utils;

src/main.rs

@@ -13,6 +13,7 @@ fn main() {
         (6, day06::day_main),
         (7, day07::day_main),
         (8, day08::day_main),
+        (9, day09::day_main),
     ]);
     let day: Option<u8> = args().nth(1).and_then(|a| a.parse().ok());
     let Some(day) = day else {