From 1d6edda98bd072271fa2baf8485563bedaf16b37 Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Tue, 13 Nov 2018 11:54:56 +0100
Subject: [PATCH] Actually commit the implementation.

---
 2016/src/day16.rs | 88 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 2016/src/day16.rs

diff --git a/2016/src/day16.rs b/2016/src/day16.rs
new file mode 100644
index 0000000..8b13d79
--- /dev/null
+++ b/2016/src/day16.rs
@@ -0,0 +1,88 @@
+use std::io;
+use std::io::prelude::*;
+use itertools::Itertools;
+use common;
+
+
+#[derive(Default)]
+pub struct Day16 {
+}
+
+impl Day16 {
+    pub fn new() -> Day16 {
+        Default::default()
+    }
+
+    fn solve(&self, input: &mut io::Read, target_size: usize) -> String {
+        let mut reader = io::BufReader::new(input);
+        let mut line = String::new();
+        reader.read_line(&mut line).expect("No input!");
+
+        let data: Vec<bool> = line.trim().chars().map(|x| x == '1').collect();
+        let filled = fill(&data, target_size);
+        let sum = checksum(&filled);
+
+        sum.iter().map(|b| if *b { '1' } else { '0' }).collect()
+    }
+}
+
+
+impl common::Solution for Day16 {
+
+    fn part1(&mut self, input: &mut io::Read) -> String {
+        self.solve(input, 272)
+    }
+
+    fn part2(&mut self, input: &mut io::Read) -> String {
+        self.solve(input, 35651584)
+    }
+}
+
+
+fn fill(initial: &[bool], size: usize) -> Vec<bool> {
+    let mut a = initial.to_vec();
+    while a.len() < size {
+        let mut b = a.clone();
+        a.push(false);
+        b.reverse();
+        a.extend(b.iter().map(|x| !x));
+    }
+
+    a.truncate(size);
+    a
+}
+
+fn checksum(initial: &[bool]) -> Vec<bool> {
+    let mut checksum = initial.to_vec();
+    while checksum.len() % 2 == 0 {
+        let mut new_checksum = Vec::new();
+        for (a, b) in checksum.into_iter().tuples() {
+            new_checksum.push(a == b);
+        }
+        checksum = new_checksum;
+    }
+    checksum
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_fill() {
+        assert_eq!(vec![true, false, false, false, false,
+                        false, true, true, true, true,
+                        false, false, true, false, false,
+                        false, false, true, true, true], fill(&[true, false, false, false, false], 20));
+    }
+
+    #[test]
+    fn test_checksum() {
+        let result = checksum(&[true, false, false, false, false,
+                              false, true, true, true, true,
+                              false, false, true, false, false,
+                              false, false, true, true, true]);
+        assert_eq!(vec![false, true, true, false, false], result);
+    }
+}