part 1

2024/day03/src/lib.rs

@@ -0,0 +1,92 @@
+use helper::{Day, Variants};
+use nom::FindSubstring;
+
+pub fn main() {
+    helper::main::<Day03>(include_str!("../input.txt"));
+}
+
+struct Day03;
+
+helper::define_variants! {
+    day => crate::Day03;
+    part1 {
+        basic => crate::part1;
+    }
+    part2 {
+        basic => crate::part2;
+    }
+}
+
+impl Day for Day03 {
+    fn part1() -> Variants {
+        part1_variants!(construct_variants)
+    }
+
+    fn part2() -> Variants {
+        part2_variants!(construct_variants)
+    }
+}
+
+fn part1(input: &str) -> u64 {
+    let mut input = input.as_bytes();
+    let mut total = 0;
+
+    fn parse_digit(input: &[u8]) -> Option<(u64, &[u8])> {
+        let mut result = 0;
+        let mut i = 0;
+        while input.len() > i && input[i].is_ascii_digit() {
+            result *= 10;
+            result += (input[i] - b'0') as u64;
+            i += 1;
+        }
+        if i == 0 {
+            return None;
+        }
+        Some((result, &input[i..]))
+    }
+
+    fn try_parse_mul(mut input: &[u8]) -> Option<(&[u8], u64)> {
+        input = &input.get(4..)?;
+        let (a, b);
+        (a, input) = parse_digit(input)?;
+        if input.get(0) != Some(&b',') {
+            return None;
+        }
+        input = &input[1..];
+        (b, input) = parse_digit(input)?;
+        if input.get(0) != Some(&b')') {
+            return None;
+        }
+        input = &input[1..];
+        Some((input, a * b))
+    }
+
+    while let Some(next) = input.find_substring("mul(") {
+        match try_parse_mul(&input[next..]) {
+            Some((new_input, val)) => {
+                total += val;
+                input = new_input;
+            }
+            None => input = &input[(next+4)..]
+        }
+    }
+
+    total
+}
+
+fn part2(_input: &str) -> u64 {
+    0
+}
+
+helper::tests! {
+    day03 Day03;
+    part1 {
+        small => 161;
+        default => 187833789;
+    }
+    part2 {
+        small => 0;
+        default => 0;
+    }
+}
+helper::benchmarks! {}