4 files changed, 80 insertions(+), 1 deletions(-)

M Cargo.lock
M Cargo.toml
A crates/day3/Cargo.toml
A crates/day3/src/main.rs

@@ 24,6 24,13 @@ dependencies = [
 ]
 
 [[package]]
+name = "day3"
+version = "0.1.0"
+dependencies = [
+ "common",
+]
+
+[[package]]
 name = "sc"
 version = "0.2.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"

@@ 1,3 1,3 @@
 [workspace]
 resolver = "3"
-members = ["crates/common", "crates/day1", "crates/day2"]
+members = ["crates/common", "crates/day1", "crates/day2", "crates/day3"]

@@ 0,0 1,7 @@
+[package]
+name = "day3"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+common = { path = "../common" }

@@ 0,0 1,65 @@
+#![no_std]
+
+use core::fmt::Write;
+
+use common::{print, read};
+
+fn main() {
+    let buf = [0u8; 65000];
+    read(buf.as_ptr(), buf.len());
+    let mut input = str::from_utf8(&buf).unwrap();
+    input = input.trim_end_matches(char::MIN);
+    input = input.trim();
+    let result_one = one(input);
+    let result_two = two(input);
+    print!(64, "one: {}\ntwo: {}\n", result_one, result_two);
+}
+
+fn one(input: &str) -> usize {
+    input
+        .split("\n")
+        .map(|bank| {
+            let mut first = char::MIN;
+            let mut first_index = 0;
+            let mut second = char::MIN;
+            let mut second_index = 0;
+
+            for (i, c) in bank.chars().enumerate() {
+                if c > first && i != bank.len() - 1 {
+                    first = c;
+                    first_index = i;
+
+                    second = char::MIN;
+                    second_index = 0;
+                } else if c > second && i > first_index {
+                    second = c;
+                    second_index = i;
+                }
+            }
+
+            let a = &bank[first_index..first_index + 1];
+            let b = &bank[second_index..second_index + 1];
+
+            let mut buf = [0; 2];
+            let c = common::format_str(&mut buf, format_args!("{}{}", a, b));
+
+            c.parse::<usize>().unwrap()
+        })
+        .sum::<usize>()
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const EXAMPLE_INPUT: &str = r#"987654321111111
+811111111111119
+234234234234278
+818181911112111"#;
+
+    #[test]
+    fn example() {
+        assert_eq!(one(EXAMPLE_INPUT), 357);
+        assert_eq!(two(EXAMPLE_INPUT), 3121910778619);
+    }
+}