From ad57cc604e983dfa7c3d1cc8b7567d5ecd6e1511 Mon Sep 17 00:00:00 2001
From: Alpha Chen <alpha.chen@gmail.com>
Date: Mon, 17 Dec 2018 14:26:23 -0800
Subject: [PATCH] [2018][rust][13.1]

---
 2018/rust/src/bin/day_14.rs | 55 +++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 2018/rust/src/bin/day_14.rs

diff --git a/2018/rust/src/bin/day_14.rs b/2018/rust/src/bin/day_14.rs
new file mode 100644
index 0000000..c7afbec
--- /dev/null
+++ b/2018/rust/src/bin/day_14.rs
@@ -0,0 +1,55 @@
+use std::error::Error;
+
+use advent_of_code::main;
+
+main!();
+
+fn solve(_input: &str) -> Result<String, Box<Error>> {
+    let elves = vec![0, 1];
+    let recipes = vec![3, 7];
+    let mut scoreboard = Scoreboard { elves, recipes };
+
+    let n = 919_901;
+    let recipes = scoreboard.find(|x| x.len() > n + 9).unwrap();
+    let score: String = recipes[n..n + 10].iter().map(|&x| x.to_string()).collect();
+
+    Ok(score)
+}
+
+#[derive(Debug)]
+struct Scoreboard {
+    elves: Vec<usize>,
+    recipes: Vec<usize>,
+}
+
+impl Iterator for Scoreboard {
+    type Item = Vec<usize>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.elves
+            .iter()
+            .map(|&x| self.recipes[x])
+            .sum::<usize>()
+            .to_string()
+            .chars()
+            .map(|x| x.to_digit(10).unwrap() as usize)
+            .for_each(|x| self.recipes.push(x));
+        self.elves = self
+            .elves
+            .iter()
+            .map(|&x| (1 + self.recipes[x] + x) % self.recipes.len())
+            .collect();
+
+        Some(self.recipes.clone())
+    }
+}
+
+#[test]
+fn test_scoreboard() {
+    let elves = vec![0, 1];
+    let recipes = vec![3, 7];
+    let mut scoreboard = Scoreboard { elves, recipes };
+
+    let recipes = scoreboard.next().unwrap();
+    assert_eq!(recipes, vec![3, 7, 1, 0]);
+}