2023: Add performance hack for day 3

Not a good idea for all kinds of strings.
jp7677 · Dec 4, 2023 · 5ee921a · 5ee921a
1 parent 42074f2
commit 5ee921a
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Showing 3 changed files with 8 additions and 1 deletion.
diff --git a/2023/src/day03.rs b/2023/src/day03.rs
@@ -109,7 +109,7 @@ fn parse_map(input: &String) -> Vec<Part> {
                 })
                 .collect::<Vec<Adjacent>>();
 
-            if i >= 1 && input.chars().nth(i - 1).unwrap_or('_').is_digit(10) {
+            if i >= 1 && char_at(input, i - 1).is_digit(10) {
                 parts.last_mut().unwrap().number.push(c);
                 parts
                     .last_mut()

diff --git a/2023/src/util/mod.rs b/2023/src/util/mod.rs
@@ -1,5 +1,7 @@
 mod days;
 mod input;
+mod strings;
 
 pub use days::DAYS;
 pub use input::read_input;
+pub use strings::char_at;
diff --git a/2023/src/util/strings.rs b/2023/src/util/strings.rs
@@ -0,0 +1,5 @@
+#[inline(always)]
+pub fn char_at(str: &str, index: usize) -> char {
+    // Not a good idea for all kinds of strings.
+    *(&str[index..index + 1].chars().nth(0).unwrap())
+}