From c5989cc613762debe698ce5a5f6f37a4c0d8387f Mon Sep 17 00:00:00 2001
From: Timothy Quilling <teqed@shatteredsky.net>
Date: Sun, 8 Dec 2024 12:18:53 -0500
Subject: [PATCH] add 2024 day7 in rust; wildcard gitignore puzzle notes

---
 .gitignore                |   3 +-
 Cargo.toml                |   4 ++
 src/2024/day7/rust/mod.rs | 103 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+), 2 deletions(-)
 create mode 100644 src/2024/day7/rust/mod.rs

diff --git a/.gitignore b/.gitignore
index dd00645..feee64f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -46,8 +46,7 @@ coverage
 input.txt
 input_example.txt
 input_example_b.txt
-prompt_a.md
-prompt_b.md
+puzzle_*.md
 
 ## Python
 # Byte-compiled / optimized / DLL files
diff --git a/Cargo.toml b/Cargo.toml
index d29df06..d8cac80 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -35,6 +35,10 @@ path = "src/2024/day5/rust/mod.rs"
 name = "2024_day6"
 path = "src/2024/day6/rust/mod.rs"
 
+[[bin]]
+name = "2024_day7"
+path = "src/2024/day7/rust/mod.rs"
+
 [lints.rust]
 unsafe_code = "forbid"
 
diff --git a/src/2024/day7/rust/mod.rs b/src/2024/day7/rust/mod.rs
new file mode 100644
index 0000000..f4eb1e0
--- /dev/null
+++ b/src/2024/day7/rust/mod.rs
@@ -0,0 +1,103 @@
+struct TestCase {
+    test_val: i64,
+    nums: Vec<i64>,
+}
+
+pub fn part_a(input: &str) -> i64 {
+    parse_input(input).iter()
+        .filter_map(|test_case| if can_create(&test_case.test_val, &test_case.nums, false) { Some(test_case.test_val) } else { None })
+        .sum()
+}
+
+pub fn part_b(input: &str) -> i64 {
+    parse_input(input).iter()
+        .filter_map(|test_case| if can_create(&test_case.test_val, &test_case.nums, true) { Some(test_case.test_val) } else { None })
+        .sum()
+}
+
+fn parse_input(input: &str) -> Vec<TestCase> {
+    input.lines()
+        .filter_map(|line| {
+            let parts: Vec<_> = line.split(": ").collect();
+            parts[0].parse::<i64>().map_or(None, |test_val| {
+                let nums = parts[1].split_whitespace()
+                    .filter_map(|s| s.parse::<i64>().ok())
+                    .collect();
+                Some(TestCase { test_val, nums })
+            })
+        })
+        .collect()
+}
+
+fn can_create(test_val: &i64, nums: &[i64], is_part_b: bool) -> bool {
+    fn evaluate(expr: &[i64], acc: i64, is_part_b: bool, test_val: i64) -> Vec<i64> {
+        if expr.is_empty() {
+            return vec![acc];
+        }
+        let first = expr[0];
+        let rest = &expr[1..];
+        let mut results = Vec::new();
+
+        if acc + first - 1 > test_val {
+            return results;
+        }
+
+        results.extend(evaluate(rest, acc + first, is_part_b, test_val));
+        results.extend(evaluate(rest, acc * first, is_part_b, test_val));
+
+        if is_part_b {
+            match format!("{}{}", acc, first).parse::<i64>() {
+                Ok(concat_result) if concat_result <= test_val => {
+                    results.extend(evaluate(rest, concat_result, is_part_b, test_val));
+                }
+                _ => {}
+            }
+        }
+
+        results
+    }
+
+    if nums.is_empty() {
+        return *test_val == 0;
+    }
+
+    let first_num = nums[0];
+    let options = evaluate(&nums[1..], first_num, is_part_b, *test_val);
+    options.contains(test_val)
+}
+
+pub fn main() {
+    let input = include_str!("../input.txt");
+    let example_input = include_str!("../input_example.txt");
+    // let example_input_b = include_str!("../input_example_b.txt");
+    let day: u8 = 7;
+    println!("Day {} Example Part A: {}", day, part_a(example_input));
+    println!("Day {} Part A: {}", day, part_a(input));
+    println!("Day {} Example Part B: {}", day, part_b(example_input));
+    println!("Day {} Part B: {}", day, part_b(input));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_a_example() {
+        let example_input = include_str!("../input_example.txt");
+        assert_eq!(part_a(example_input), 3749);
+    }
+    #[test]
+    fn test_part_a() {
+        let input = include_str!("../input.txt");
+        assert_eq!(part_a(input), 3312271365652);
+    }
+    #[test]
+    fn test_part_b_example() {
+        let example_input_b = include_str!("../input_example.txt");
+        assert_eq!(part_b(example_input_b), 11387);
+    }
+    #[test]
+    fn test_part_b() {
+        let input = include_str!("../input.txt");
+        assert_eq!(part_b(input), 509463489296712);
+    }
+}
-- 
2.51.2