thats it

2024/day01/src/lib.rs

@@ -21,6 +21,7 @@ helper::define_variants! {
         faster_parsing => crate::part2_parsing;
         array => crate::part2_array;
         μopt_parsing => crate::part2_μopt_parsing;
+        part2_bytes => crate::part2_bytes;
     }
 }
 
@@ -177,42 +178,90 @@ fn part2_array(input: &str) -> u64 {
     score
 }
 
-
 fn part2_μopt_parsing(input: &str) -> u64 {
+    assert_eq!(input.as_bytes().last(), Some(&b'\n'));
+
     const BIGGEST_ELEMENT: usize = 100_000;
     let mut right_map = vec![0_u16; BIGGEST_ELEMENT];
-    let mut left = Vec::with_capacity(input.len() / 8);
+    let mut left = Vec::with_capacity(input.len());
+
+    let digit_len = input.as_bytes().iter().position(|b| *b == b' ').unwrap();
+    let line_len = 2 * digit_len + 3 + 1;
+
+    fn parse_digit(input: &str, len: usize) -> u64 {
+        let mut result = 0;
+        for i in 0..len {
+            result *= 10;
+            result += (input.as_bytes()[i] - b'0') as u64;
+        }
+        result
+    }
 
     let mut input = input;
-    loop {
-        let Some(space) = input.as_bytes().iter().position(|b| *b == b' ') else {
-            break;
-        };
-        let number = input[..space].parse::<u64>().unwrap();
-        left.push(number);
-        input = &input[(space + 3)..];
-        let Some(newline) = input.as_bytes().iter().position(|b| *b == b'\n') else {
-            break;
-        };
-        let number = input[..space].parse::<u64>().unwrap();
+    while input.len() >= line_len {
+        let number = parse_digit(input, digit_len);
+
+        left.push(number as u32);
+        input = &input[(digit_len + 3)..];
+
+        let number = parse_digit(input, digit_len);
         right_map[number as usize] += 1;
-        input = &input[newline..];
-        // handle lack of trailing newline
-        if !input.is_empty() {
-            input = &input[1..];
-        }
+        input = &input[digit_len..];
+        input = &input[1..];
     }
 
     let mut score = 0;
 
     for number in left {
         let occurs = right_map[number as usize];
-        score += number * (occurs as u64);
+        score += (number as u64) * (occurs as u64);
     }
 
     score
 }
 
+fn part2_bytes(input: &str) -> u64 {
+    let input = input.as_bytes();
+    assert_eq!(input.last(), Some(&b'\n'));
+
+    const BIGGEST_ELEMENT: usize = 100_000;
+    let mut right_map = vec![0_u16; BIGGEST_ELEMENT];
+    let mut left = Vec::<u32>::with_capacity(input.len());
+
+    let digit_len = input.iter().position(|b| *b == b' ').unwrap();
+    let line_len = 2 * digit_len + 3 + 1;
+
+    fn parse_digit(input: &[u8], len: usize) -> u32 {
+        let mut result = 0;
+        for i in 0..len {
+            result *= 10;
+            result += (unsafe { input.get_unchecked(i) } - b'0') as u32;
+        }
+        result
+    }
+
+    let mut input = input;
+    while input.len() >= line_len {
+        let number = parse_digit(input, digit_len);
+
+        left.push(number);
+        input = unsafe { &input.get_unchecked((digit_len + 3)..) };
+
+        let number = parse_digit(input, digit_len);
+        right_map[number as usize] += 1;
+        input = unsafe { &input.get_unchecked((digit_len + 1)..) };
+    }
+
+    let mut score = 0;
+
+    for number in left {
+        let occurs = right_map[number as usize];
+        score += number * (occurs as u32);
+    }
+
+    score as u64
+}
+
 helper::tests! {
     day01 Day01;
     part1 {