Day11 - part 1

diff --git a/src/day11.rs b/src/day11.rs
new file mode 100644 (file)
index 0000000..ea26498
--- /dev/null
+++ b/src/day11.rs
@@ -0,0 +1,89 @@
+use std::error::Error;
+use std::path::Path;
+
+fn split_in_two(value: u64) -> Option<(u64, u64)> {
+    let n_digits = value.ilog10() + 1;
+    if n_digits % 2 == 0 {
+        let p = 10_u64.pow(n_digits / 2);
+        return Some((value / p, value % p));
+    }
+    else {
+        return None;
+    }
+}
+
+fn count_stones(value: u64, blinks: u32) -> u32 {
+    if blinks == 0 {
+        return 1;
+    }
+    else if value == 0 {
+        return count_stones(1, blinks - 1);
+    }
+    else {
+        if let Some((r, l)) = split_in_two(value) {
+            return count_stones(r, blinks - 1) + count_stones(l, blinks - 1);
+        }
+        else {
+            return count_stones(value * 2024, blinks - 1);
+        }
+    }
+}
+
+fn run_part1(input: &str, blinks: u32) -> Result<u32, Box<dyn Error>> {
+    println!("Running {} - part 1", get_day());
+
+    let res = input.split_whitespace()
+        .map(|v| v.parse::<u64>().unwrap())
+        .map(|v| count_stones(v, blinks))
+        .sum::<u32>();
+
+    Ok(res)
+}
+
+fn run_part2(input: &str) -> Result<u32, Box<dyn Error>> {
+    println!("Running {} - part 2", get_day());
+
+    Ok(0)
+}
+
+pub fn run(input: &str) -> Result<(), Box<dyn Error>> {
+    let res = run_part1(input, 25)?;
+    println!("{res}");
+
+    let res = run_part2(input)?;
+    println!("{res}");
+
+    Ok(())
+}
+
+fn get_day() -> String {
+    let filename = file!();
+    Path::new(filename).file_stem().unwrap().to_str().unwrap().to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    static TEXT_INPUT_0: &str = "\
+0 1 10 99 999";
+    static TEXT_INPUT: &str = "\
+125 17";
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(7, run_part1(TEXT_INPUT_0, 1).unwrap());
+        assert_eq!(3, run_part1(TEXT_INPUT, 1).unwrap());
+        assert_eq!(4, run_part1(TEXT_INPUT, 2).unwrap());
+        assert_eq!(5, run_part1(TEXT_INPUT, 3).unwrap());
+        assert_eq!(9, run_part1(TEXT_INPUT, 4).unwrap());
+        assert_eq!(13, run_part1(TEXT_INPUT, 5).unwrap());
+        assert_eq!(22, run_part1(TEXT_INPUT, 6).unwrap());
+        assert_eq!(55312, run_part1(TEXT_INPUT, 25).unwrap());
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(0, run_part2(TEXT_INPUT).unwrap());
+    }
+}

diff --git a/src/main.rs b/src/main.rs
index 52ca4cc28661310076756c5328ed6398938d9964..dd9eed2c18ce8b98f46591f4ee4b969503f65e71 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -14,6 +14,7 @@ pub mod day07;
 pub mod day08;
 pub mod day09;
 pub mod day10;
+pub mod day11;
 
 fn main() {
     let args: Vec<String> = env::args().collect();
@@ -46,6 +47,7 @@ fn run(day: &str, input_file: &str) -> Result<(), Box<dyn Error>> {
         "day08" => day08::run(&input)?,
         "day09" => day09::run(&input)?,
         "day10" => day10::run(&input)?,
+        "day11" => day11::run(&input)?,
         _ => return Err(format!("unknown or unimplemented day \"{day}\"").into()),
     }
     Ok(())