solve year 2023 day 04

src/lib.rs

@@ -23,4 +23,5 @@ pub mod year2023 {
     pub mod day01;
     pub mod day02;
     pub mod day03;
+    pub mod day04;
 }

src/main.rs

@@ -98,5 +98,6 @@ fn year2023() -> Vec<Solution> {
         solution!(year2023, day01),
         solution!(year2023, day02),
         solution!(year2023, day03),
+        solution!(year2023, day04),
     ]
 }

src/year2023/day03.rs

@@ -11,7 +11,7 @@ fn parse_nums(input: &str) -> BTreeMap<Dim<[i64; 2]>, u32> {
             if c.is_ascii_digit() {
                 let mut num = (c as u8 - b'0') as u32;
                 let mut end = x;
-                while let Some((idx, c)) = line.next() {
+                for (idx, c) in line.by_ref() {
                     if c.is_ascii_digit() {
                         num = num * 10 + (c as u8 - b'0') as u32;
                         end = idx;

src/year2023/day04.rs

@@ -0,0 +1,48 @@
+use crate::util::parse::ParseExt;
+
+pub fn part1(input: &str) -> impl std::fmt::Display {
+    input
+        .lines()
+        .map(|line| {
+            let (_, rest) = line.split_once(':').unwrap();
+            let (winning, numbers) = rest.split_once('|').unwrap();
+            let winning = winning.u32s().collect::<Vec<_>>();
+            let numbers = numbers.u32s().filter(|n| winning.contains(n)).count() as u32;
+            (numbers > 0).then(|| 2u32.pow(numbers - 1)).unwrap_or(0)
+        })
+        .sum::<u32>()
+}
+
+pub fn part2(input: &str) -> impl std::fmt::Display {
+    let lines = input.lines().collect::<Vec<_>>();
+    let len = lines.len();
+    let mut mults = vec![1; len];
+
+    lines
+        .iter()
+        .enumerate()
+        .map(|(i, line)| {
+            let (_, rest) = line.split_once(':').unwrap();
+            let (winning, numbers) = rest.split_once('|').unwrap();
+            let winning = winning.u32s().collect::<Vec<_>>();
+            let numbers = numbers.u32s().filter(|n| winning.contains(n)).count();
+            let mul = mults[i];
+            mults
+                .iter_mut()
+                .take((i + numbers + 1).min(len))
+                .skip(i + 1)
+                .for_each(|c| *c += mul);
+            mul
+        })
+        .sum::<u32>()
+}
+
+#[test]
+fn test_part1() {
+    assert_eq!("", part1("").to_string())
+}
+
+#[test]
+fn test_part2() {
+    assert_eq!("", part2("").to_string())
+}