From 6d557c35cf3b4dea772a1b445a81f299f9084c33 Mon Sep 17 00:00:00 2001
From: Jan-Bulthuis <git@bulthuis.dev>
Date: Sat, 7 Dec 2024 14:36:19 +0100
Subject: [PATCH] day7

---
 aoc_2024/src/day7.rs | 90 ++++++++++++++++++++++++++++++++++++++++++++
 aoc_2024/src/lib.rs  |  7 ++--
 2 files changed, 94 insertions(+), 3 deletions(-)
 create mode 100644 aoc_2024/src/day7.rs

diff --git a/aoc_2024/src/day7.rs b/aoc_2024/src/day7.rs
new file mode 100644
index 0000000..eb4ea98
--- /dev/null
+++ b/aoc_2024/src/day7.rs
@@ -0,0 +1,90 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use nom::{
+    bytes::complete::tag,
+    character::complete::{newline, space1, u64 as parse_u64},
+    error::Error,
+    multi::separated_list1,
+    sequence::separated_pair,
+};
+
+type Input = Vec<(u64, Vec<u64>)>;
+
+#[aoc_generator(day7)]
+fn parse(input: &str) -> Input {
+    separated_list1(
+        newline::<&str, Error<&str>>,
+        separated_pair(parse_u64, tag(": "), separated_list1(space1, parse_u64)),
+    )(input)
+    .unwrap()
+    .1
+}
+
+#[aoc(day7, part1)]
+fn part1(input: &Input) -> usize {
+    input
+        .iter()
+        .filter(|v| part1_test(v.1[0], v.0, &v.1[1..]))
+        .fold(0, |acc, v| acc + v.0 as usize)
+}
+
+fn part1_test(curr: u64, target: u64, numbers: &[u64]) -> bool {
+    if curr > target {
+        false
+    } else if numbers.is_empty() {
+        curr == target
+    } else {
+        let num = numbers[0];
+        let rest = &numbers[1..];
+        part1_test(curr + num, target, rest) || part1_test(curr * num, target, rest)
+    }
+}
+
+#[aoc(day7, part2)]
+fn part2(input: &Input) -> usize {
+    input
+        .iter()
+        .filter(|v| part2_test(v.1[0], v.0, &v.1[1..]))
+        .fold(0, |acc, v| acc + v.0 as usize)
+}
+
+fn concat(a: u64, b: u64) -> u64 {
+    let digits = b.ilog10() + 1;
+    a * 10u64.pow(digits) + b
+}
+
+fn part2_test(curr: u64, target: u64, numbers: &[u64]) -> bool {
+    if curr > target {
+        false
+    } else if numbers.is_empty() {
+        curr == target
+    } else {
+        let num = numbers[0];
+        let rest = &numbers[1..];
+        part2_test(curr + num, target, rest)
+            || part2_test(curr * num, target, rest)
+            || part2_test(concat(curr, num), target, rest)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&parse("190: 10 19\n3267: 81 40 27\n83: 17 5\n156: 15 6\n7290: 6 8 6 15\n161011: 16 10 13\n192: 17 8 14\n21037: 9 7 18 13\n292: 11 6 16 20")), 3749);
+        assert_eq!(
+            part1(&parse(include_str!("../input/2024/day7.txt"))),
+            3598800864292
+        );
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&parse("190: 10 19\n3267: 81 40 27\n83: 17 5\n156: 15 6\n7290: 6 8 6 15\n161011: 16 10 13\n192: 17 8 14\n21037: 9 7 18 13\n292: 11 6 16 20")), 11387);
+        assert_eq!(
+            part2(&parse(include_str!("../input/2024/day7.txt"))),
+            340362529351427
+        );
+    }
+}
diff --git a/aoc_2024/src/lib.rs b/aoc_2024/src/lib.rs
index 23ec5de..06ec462 100644
--- a/aoc_2024/src/lib.rs
+++ b/aoc_2024/src/lib.rs
@@ -1,9 +1,10 @@
-mod day6;
-mod day5;
-mod day4;
 mod day1;
 mod day2;
 mod day3;
+mod day4;
+mod day5;
+mod day6;
+mod day7;
 
 extern crate aoc_runner;