[rust][10.0]

rust/input/day_10.txt

@@ -0,0 +1 @@
+1113122113

rust/src/day_10.rs

@@ -0,0 +1,59 @@
+#[test]
+fn test_day_10() {
+    let mut foo = LookAndSay { seq: vec![2, 1, 1] };
+    assert_eq!(vec![1, 2, 2, 1], foo.next().unwrap());
+
+    foo = LookAndSay { seq: vec![1] };
+    assert_eq!(vec![1, 1], foo.next().unwrap());
+    assert_eq!(vec![2, 1], foo.next().unwrap());
+    assert_eq!(vec![1, 2, 1, 1], foo.next().unwrap());
+    assert_eq!(vec![1, 1, 1, 2, 2, 1], foo.next().unwrap());
+    assert_eq!(vec![3, 1, 2, 2, 1, 1], foo.next().unwrap());
+}
+
+pub fn solve(input: &str) -> usize {
+    let seq = input
+        .chars()
+        .map(|c| c.to_digit(10).unwrap() as usize)
+        .collect::<Vec<usize>>();
+    let mut look_and_say = LookAndSay { seq: seq };
+
+    for _ in 0..40  {
+        look_and_say.next();
+    }
+
+    look_and_say.seq.len()
+}
+
+struct LookAndSay {
+    seq: Vec<usize>,
+}
+
+impl Iterator for LookAndSay {
+    type Item = Vec<usize>;
+
+    fn next(&mut self) -> Option<Vec<usize>> {
+        let mut s = Vec::new();
+
+        let mut digit = self.seq[0];
+        let mut count = 0;
+
+        for &i in &self.seq {
+            if i != digit {
+                s.push(count);
+                s.push(digit);
+
+                digit = i;
+                count = 1;
+            } else {
+                count += 1;
+            }
+        }
+        s.push(count);
+        s.push(digit);
+
+        self.seq = s.clone();
+
+        Some(s)
+    }
+}

rust/src/lib.rs

@@ -13,3 +13,4 @@ pub mod day_06;
 pub mod day_07;
 pub mod day_08;
 pub mod day_09;
+pub mod day_10;

rust/src/main.rs

@@ -7,5 +7,5 @@ use advent_of_code::*;
 fn main() {
     let mut input = String::new();
     io::stdin().read_to_string(&mut input).ok();
-    println!("{}", day_09::solve(&input));
+    println!("{}", day_10::solve(&input));
 }