1 files changed, 82 insertions, 0 deletions
diff --git a/2023/rs/code/five/src/main.rs b/2023/rs/code/five/src/main.rs
new file mode 100644
index 0000000..79ba943
--- /dev/null
+++ b/2023/rs/code/five/src/main.rs
@@ -0,0 +1,82 @@
+#![feature(iter_array_chunks)]
+
+use nom::{Parser, IResult, Finish};
+use nom::character::complete::*;
+use nom::bytes::complete::*;
+use nom::sequence::*;
+use nom::multi::*;
+
+use std::io::Write;
+
+static INPUT: &str = include_str!("input.txt");
+
+#[derive(Debug, Copy, Clone)]
+struct Entry {
+  source_start: u32,
+  dest_start: u32,
+  len: u32
+}
+
+fn parse(i: &str) -> IResult<&str, (Vec<u32>, Vec<Vec<Entry>>)> {
+  let (i, (_, seeds, mut entries)) = tuple((
+    tag("seeds: "),
+    separated_list1(tag(" "), digit1.map(|s: &str| s.parse().unwrap())),
+    many1(preceded(
+      tuple((line_ending, line_ending, not_line_ending, line_ending)),
+      separated_list1(
+        line_ending,
+        tuple((
+          digit1,
+          tag(" "),
+          digit1,
+          tag(" "),
+          digit1))
+          .map(|(a, _, b, _, c): (&str, _, &str, _, &str)|
+            Entry { dest_start: a.parse().unwrap(), source_start: b.parse().unwrap(), len: c.parse().unwrap() }))))))
+    (i)?;
+
+  for entry in &mut entries {
+    entry.sort_by_key(|e| e.source_start);
+  }
+
+  Ok((i, (seeds, entries)))
+}
+
+fn main() {
+  let (seeds, entries) = parse(INPUT).finish().unwrap().1;
+
+  let map_seed = |s: u32|
+    entries.iter().fold(
+      s,
+      |s, el| {
+        let entry = el.iter().cloned().find(
+          |i| i.source_start <= s && s - i.source_start < i.len)
+          .unwrap_or(Entry { source_start: 0, dest_start: 0, len: u32::MAX });
+        s - entry.source_start + entry.dest_start
+      });
+
+
+  let min_loc = seeds.iter().cloned().map(map_seed).min().unwrap();
+  println!("Minimum `location`: {min_loc}");
+
+  // [12:48 AM] got p1
+  // [12:48 AM] oh this sucks
+  // [12:50 AM] do i just
+  // [12:50 AM] brute force it
+  // [12:50 AM] i could like
+  // [12:50 AM] write something clever here
+  // [12:51 AM] like i think i could do something like lifting the mapping between the layers and creating one final mapping, and then just checking against that
+  // [12:51 AM] and just finding the lowest start number within the bounds of all the seed ranges
+  // [12:51 AM] but i dont feel like doing that
+
+  #[cfg(debug_assertions)]
+  eprintln!("Warning: Debug build detected! This next bit takes a while, so I'd suggest compiling `--release`.");
+
+  let min_loc_ranged = seeds.iter().array_chunks::<2>()
+    .inspect(|[a, b]| { print!("\x1B[2KChecking {} => {}...\r", *a, *a + *b); std::io::stdout().flush().unwrap(); })
+    .flat_map(|[a, b]| *a..(*a+*b))
+    .map(map_seed)
+    .min().unwrap();
+
+  println!("Minimum `location` within ranges: {min_loc_ranged}");
+}