From 2a96c16b4b63973d0f2a0132615690fad2c8ba10 Mon Sep 17 00:00:00 2001
From: Jack Kinsey <j.jameskinsey@gmail.com>
Date: Tue, 10 Dec 2024 21:59:14 -0500
Subject: [PATCH] Complete day 9 part 1

---
 src/day09.rs | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.rs  |   6 +--
 2 files changed, 127 insertions(+), 3 deletions(-)
 create mode 100644 src/day09.rs

diff --git a/src/day09.rs b/src/day09.rs
new file mode 100644
index 0000000..e80700f
--- /dev/null
+++ b/src/day09.rs
@@ -0,0 +1,124 @@
+fn input() -> &'static str {
+    include_str!("../input/day09.txt")
+}
+
+type DiskMap = Option<u64>;
+
+fn parse(input: &str) -> Vec<DiskMap> {
+    input
+        .trim()
+        .chars()
+        .zip(0..)
+        .flat_map(|(c, i)| {
+            let n: u64 = c.to_string().parse().unwrap();
+            if i % 2 == 0 {
+                vec![Some(i / 2); n.try_into().unwrap()]
+            } else {
+                vec![None; n.try_into().unwrap()]
+            }
+        })
+        .collect()
+}
+
+fn fragment(disk: &mut Vec<DiskMap>) {
+    let mut ptr = 0;
+    loop {
+        while ptr < disk.len() && disk[ptr].is_some() {
+            ptr += 1;
+        }
+        if ptr < disk.len() {
+            disk[ptr] = disk.pop().unwrap();
+        } else {
+            break;
+        }
+    }
+}
+
+fn checksum(disk: &[DiskMap]) -> u64 {
+    disk.iter()
+        .zip(0..)
+        .map(|(n, i)| match n {
+            Some(n) => n * i,
+            None => 0,
+        })
+        .sum()
+}
+
+pub fn part1() {
+    let mut map = parse(input());
+    fragment(&mut map);
+    let n = checksum(&map);
+    println!("Day 9 Part 1: {}", n);
+}
+
+pub fn part2() {
+    let n = 0;
+    println!("Day 9 Part 2: {}", n);
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const INPUT_STR: &str = concat!("2333133121414131402\n");
+
+    #[rustfmt::skip]
+    #[test]
+    fn test_parse() {
+        assert_eq!(
+            parse(INPUT_STR),
+            vec![
+                Some(0), Some(0),
+                None, None, None,
+                Some(1), Some(1), Some(1),
+                None, None, None,
+                Some(2),
+                None, None, None,
+                Some(3), Some(3), Some(3),
+                None,
+                Some(4), Some(4),
+                None,
+                Some(5), Some(5), Some(5), Some(5),
+                None,
+                Some(6), Some(6), Some(6), Some(6),
+                None,
+                Some(7), Some(7), Some(7),
+                None,
+                Some(8), Some(8), Some(8), Some(8),
+                Some(9), Some(9)
+            ],
+        )
+    }
+
+    #[rustfmt::skip]
+    #[test]
+    fn test_fragment() {
+        let mut map = parse(INPUT_STR);
+        fragment(&mut map);
+        assert_eq!(
+            map,
+            vec![
+                Some(0), Some(0),
+                Some(9), Some(9),
+                Some(8),
+                Some(1), Some(1), Some(1),
+                Some(8), Some(8), Some(8),
+                Some(2),
+                Some(7), Some(7), Some(7),
+                Some(3), Some(3), Some(3),
+                Some(6),
+                Some(4), Some(4),
+                Some(6),
+                Some(5), Some(5), Some(5), Some(5),
+                Some(6), Some(6),
+            ],
+        )
+    }
+
+    #[test]
+    fn test_checksum() {
+        let mut map = parse(INPUT_STR);
+        fragment(&mut map);
+        assert_eq!(checksum(&map), 1928)
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 879fa54..0a184da 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,7 +6,7 @@ pub mod day05;
 pub mod day06;
 pub mod day07;
 pub mod day08;
-// pub mod day09;
+pub mod day09;
 // pub mod day10;
 // pub mod day11;
 // pub mod day12;
@@ -26,7 +26,7 @@ pub mod day08;
 
 type Part = fn();
 
-const DAYS: [(Part, Part); 8] = [
+const DAYS: [(Part, Part); 9] = [
     (day01::part1 as fn(), day01::part2 as fn()),
     (day02::part1 as fn(), day02::part2 as fn()),
     (day03::part1 as fn(), day03::part2 as fn()),
@@ -35,7 +35,7 @@ const DAYS: [(Part, Part); 8] = [
     (day06::part1 as fn(), day06::part2 as fn()),
     (day07::part1 as fn(), day07::part2 as fn()),
     (day08::part1 as fn(), day08::part2 as fn()),
-    // (day09::part1 as fn(), day09::part2 as fn()),
+    (day09::part1 as fn(), day09::part2 as fn()),
     // (day10::part1 as fn(), day10::part2 as fn()),
     // (day11::part1 as fn(), day11::part2 as fn()),
     // (day12::part1 as fn(), day12::part2 as fn()),
-- 
2.38.5