Implement 2022 day 12

2022/inputs/12.txt

@@ -0,0 +1,41 @@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2022/src/day12.rs

@@ -1,9 +1,128 @@
+use std::collections::VecDeque;
+
+use anyhow::Context;
 use anyhow::Result;
 
-pub fn part1(_input: &[u8]) -> Result<String> {
-    anyhow::bail!("not implemented")
+fn can_travel(from: u8, to: u8) -> bool {
+    match (from, to) {
+        (b'S', b'a'..=b'z') => true,
+        (b'y'..=b'z', b'E') => true,
+        (b'a'..=b'z', b'a'..=b'z') => to <= from || to - from == 1,
+        _ => false,
+    }
 }
 
-pub fn part2(_input: &[u8]) -> Result<String> {
-    anyhow::bail!("not implemented")
+pub fn part1(input: &[u8]) -> Result<String> {
+    let width = input
+        .iter()
+        .position(|&c| c == b'\n')
+        .context("No newlines in input")?
+        + 1;
+
+    let starting_pos = input
+        .iter()
+        .position(|&c| c == b'S')
+        .context("Could not find starting position")?;
+
+    let mut visited = vec![false; input.len()];
+
+    let mut todo = VecDeque::new();
+    todo.push_back((0, starting_pos));
+
+    while let Some((dist, pos)) = todo.pop_front() {
+        if input[pos] == b'E' {
+            return Ok(dist.to_string());
+        }
+
+        let mut add_todo = |new: usize| {
+            if can_travel(input[pos], input[new]) && !visited[new] {
+                visited[new] = true;
+                todo.push_back((dist + 1, new));
+            }
+        };
+
+        if pos % width != 0 {
+            add_todo(pos - 1);
+        }
+
+        if pos % width != width - 1 {
+            add_todo(pos + 1)
+        }
+
+        if pos >= width {
+            add_todo(pos - width);
+        }
+
+        if pos + width < input.len() {
+            add_todo(pos + width);
+        }
+    }
+
+    anyhow::bail!("Did not find a valid route")
+}
+
+pub fn part2(input: &[u8]) -> Result<String> {
+    let width = input
+        .iter()
+        .position(|&c| c == b'\n')
+        .context("No newlines in input")?
+        + 1;
+
+    let starting_pos = input
+        .iter()
+        .position(|&c| c == b'E')
+        .context("Could not find starting position")?;
+
+    let mut visited = vec![false; input.len()];
+
+    let mut todo = VecDeque::new();
+    todo.push_back((0, starting_pos));
+
+    while let Some((dist, pos)) = todo.pop_front() {
+        if input[pos] == b'a' || input[pos] == b'S' {
+            return Ok(dist.to_string());
+        }
+
+        let mut add_todo = |new: usize| {
+            if can_travel(input[new], input[pos]) && !visited[new] {
+                visited[new] = true;
+                todo.push_back((dist + 1, new));
+            }
+        };
+
+        if pos % width != 0 {
+            add_todo(pos - 1);
+        }
+
+        if pos % width != width - 1 {
+            add_todo(pos + 1);
+        }
+
+        if pos >= width {
+            add_todo(pos - width);
+        }
+
+        if pos + width < input.len() {
+            add_todo(pos + width);
+        }
+    }
+
+    anyhow::bail!("Did not find a valid route")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE: &[u8] = include_bytes!("samples/12.txt");
+
+    #[test]
+    fn sample_part1() {
+        assert_eq!(part1(SAMPLE).unwrap(), "31")
+    }
+
+    #[test]
+    fn sample_part2() {
+        assert_eq!(part2(SAMPLE).unwrap(), "29")
+    }
 }

2022/src/samples/12.txt

@@ -0,0 +1,5 @@
+Sabqponm
+abcryxxl
+accszExk
+acctuvwj
+abdefghi