From c6718f86e51f7d64f81b0ec53213774097bb8655 Mon Sep 17 00:00:00 2001
From: Louis Vallat <contact@louis-vallat.dev>
Date: Thu, 12 Dec 2024 11:51:49 +0100
Subject: [PATCH] feat: added day 11 part 1 and 2

Signed-off-by: Louis Vallat <contact@louis-vallat.dev>
---
 .gitea/workflows/build_and_run.yml |  2 +-
 day11/Cargo.toml                   |  6 +++
 day11/src/main.rs                  | 70 ++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 1 deletion(-)
 create mode 100644 day11/Cargo.toml
 create mode 100644 day11/src/main.rs

diff --git a/.gitea/workflows/build_and_run.yml b/.gitea/workflows/build_and_run.yml
index 2f2b049..db09ccd 100644
--- a/.gitea/workflows/build_and_run.yml
+++ b/.gitea/workflows/build_and_run.yml
@@ -11,7 +11,7 @@ jobs:
     name: Challenge for day
     strategy:
       matrix:
-        day_number: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+        day_number: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
     runs-on: rust-bookworm
     steps:
       - name: Check out repository code
diff --git a/day11/Cargo.toml b/day11/Cargo.toml
new file mode 100644
index 0000000..d3a547b
--- /dev/null
+++ b/day11/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "day11"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/day11/src/main.rs b/day11/src/main.rs
new file mode 100644
index 0000000..e373b2f
--- /dev/null
+++ b/day11/src/main.rs
@@ -0,0 +1,70 @@
+use std::collections::HashMap;
+use std::{env, fs};
+
+fn read_input(path: &str) -> String {
+    fs::read_to_string(path).expect("Cannot read file.")
+}
+
+fn parse_input(input: &str) -> Vec<usize> {
+    input
+        .split_whitespace()
+        .map(|x| x.parse().unwrap())
+        .collect()
+}
+
+fn compute_stone(
+    value: usize,
+    remaining_blinks: usize,
+    cache: &mut HashMap<(usize, usize), usize>,
+) -> usize {
+    if cache.contains_key(&(value, remaining_blinks)) {
+        return *cache.get(&(value, remaining_blinks)).unwrap();
+    }
+
+    if remaining_blinks == 0 {
+        return 1;
+    }
+
+    let result;
+    if value == 0 {
+        result = compute_stone(1, remaining_blinks - 1, cache);
+    } else {
+        let digit = value.to_string();
+        if digit.len() % 2 == 0 {
+            let split = digit.split_at(digit.len() / 2);
+            result = compute_stone(split.0.parse().unwrap(), remaining_blinks - 1, cache)
+                + compute_stone(split.1.parse().unwrap(), remaining_blinks - 1, cache);
+        } else {
+            result = compute_stone(value * 2024, remaining_blinks - 1, cache);
+        }
+    };
+
+    cache.insert((value, remaining_blinks), result);
+    result
+}
+
+fn part_1(stones: &Vec<usize>, cache: &mut HashMap<(usize, usize), usize>) -> usize {
+    stones
+        .iter()
+        .map(|stone| compute_stone(*stone, 25, cache))
+        .sum()
+}
+
+fn part_2(stones: &Vec<usize>, cache: &mut HashMap<(usize, usize), usize>) -> usize {
+    stones
+        .iter()
+        .map(|stone| compute_stone(*stone, 75, cache))
+        .sum()
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    for arg in args.iter().skip(1) {
+        let input = read_input(&arg);
+        let stones = parse_input(&input);
+        let mut cache = HashMap::new();
+        println!("[{}]", &arg);
+        println!("\t[Part 1] => Answer is '{}'.", part_1(&stones, &mut cache));
+        println!("\t[Part 2] => Answer is '{}'.", part_2(&stones, &mut cache));
+    }
+}