From f8c6f4e01f79155b102d03a5b88a044caf293287 Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Mon, 12 Dec 2022 22:46:30 +0100
Subject: [PATCH] Refactor out common code

---
 2022/src/day12.rs | 68 +++++++++++++----------------------------------
 1 file changed, 19 insertions(+), 49 deletions(-)

diff --git a/2022/src/day12.rs b/2022/src/day12.rs
index d3816f8..b625e81 100644
--- a/2022/src/day12.rs
+++ b/2022/src/day12.rs
@@ -14,7 +14,12 @@ fn can_travel(from: u8, to: u8) -> bool {
     }
 }
 
-pub fn part1(input: &[u8]) -> Result<String> {
+fn parts_common(
+    input: &[u8],
+    starting_symbol: u8,
+    is_end: impl Fn(u8) -> bool,
+    accessible: impl Fn(u8, u8) -> bool,
+) -> Result<String> {
     let width = input
         .iter()
         .position(|&c| c == b'\n')
@@ -23,7 +28,7 @@ pub fn part1(input: &[u8]) -> Result<String> {
 
     let starting_pos = input
         .iter()
-        .position(|&c| c == b'S')
+        .position(|&c| c == starting_symbol)
         .context("Could not find starting position")?;
 
     let mut visited = IndexSet::with_capacity(input.len());
@@ -32,12 +37,12 @@ pub fn part1(input: &[u8]) -> Result<String> {
     todo.push_back((0, starting_pos));
 
     while let Some((dist, pos)) = todo.pop_front() {
-        if input[pos] == b'E' {
+        if is_end(input[pos]) {
             return Ok(dist.to_string());
         }
 
         let mut add_todo = |new: usize| {
-            if can_travel(input[pos], input[new]) && visited.insert(new) {
+            if accessible(input[pos], input[new]) && visited.insert(new) {
                 todo.push_back((dist + 1, new));
             }
         };
@@ -62,52 +67,17 @@ pub fn part1(input: &[u8]) -> Result<String> {
     anyhow::bail!("Did not find a valid route")
 }
 
+pub fn part1(input: &[u8]) -> Result<String> {
+    parts_common(input, b'S', |b| b == b'E', can_travel)
+}
+
 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 = IndexSet::with_capacity(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.insert(new) {
-                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")
+    parts_common(
+        input,
+        b'E',
+        |b| b == b'a' || b == b'S',
+        |a, b| can_travel(b, a),
+    )
 }
 
 #[cfg(test)]