solve: day6

Author: tom-anders

Cargo.toml

@@ -2,7 +2,7 @@
 resolver = "2"
 members = [
     "aoc_lib/aoc_derive",
-    "aoc_lib/utils", "day1", "day2", "day3", "day4", "day5",
+    "aoc_lib/utils", "day1", "day2", "day3", "day4", "day5", "day6",
 ]
 
 [workspace.dependencies]

aoc_lib

@@ -0,0 +1,18 @@
+[package]
+name = "day6"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+aoc_derive.path = '../aoc_lib/aoc_derive'
+utils.path = '../aoc_lib/utils'
+derive_more.workspace = true
+itertools.workspace = true
+lazy-regex.workspace = true
+parse-display.workspace = true
+rayon.workspace = true
+regex.workspace = true
+num.workspace = true
+
+[dev-dependencies]
+pretty_assertions.workspace = true

day6/Cargo.toml

@@ -0,0 +1,53 @@
+use aoc_derive::aoc_main;
+use itertools::Itertools;
+use utils::*;
+
+#[aoc_main]
+fn solve(input: Input) -> impl Into<Solution> {
+    (
+        input
+            .str_grid()
+            .cols()
+            .map(|col| {
+                let mut col = col.rev();
+                let (_, op) = col.next().unwrap();
+                col.map(|(_, n)| n.parse_usize())
+                    .reduce(|acc, n| if *op == "+" { acc + n } else { acc * n })
+                    .unwrap()
+            })
+            .sum_usize(),
+        input
+            .char_grid()
+            .cols()
+            .map(|col| col.values().copied().collect_vec())
+            .chunk_by(|col| col.iter().all(|&c| c == ' '))
+            .into_iter()
+            .filter_map(|(is_whitespace, cols)| (!is_whitespace).then_some(cols.collect_vec()))
+            .map(|cols| {
+                let op = *cols.first().unwrap().last().unwrap();
+                cols.into_iter()
+                    .map(|col| col.iter().copied().fold_chars_to_number() as usize)
+                    .reduce(|acc, n| if op == '+' { acc + n } else { acc * n })
+                    .unwrap()
+            })
+            .sum_usize(),
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_examples() {
+        pretty_assertions::assert_eq!(
+            solve(Input::from_str_no_trim(
+                r#"123 328  51 64 
+ 45 64  387 23 
+  6 98  215 314
+*   +   *   +  "#,
+            ))
+            .into(),
+            (4277556, 3263827).into(),
+        );
+    }
+}