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authorJune McEnroe <june@causal.agency>2017-12-23 19:42:36 -0500
committerJune McEnroe <june@causal.agency>2020-11-22 00:14:25 -0500
commit3037ee1443a892a1c10b4d232e66c3b478d3d54b (patch)
tree0eedce76946308be282d3c724f8fa6136e3d4347 /2017
parentDay 13, part 2 (diff)
downloadaoc-3037ee1443a892a1c10b4d232e66c3b478d3d54b.tar.gz
aoc-3037ee1443a892a1c10b4d232e66c3b478d3d54b.zip
Day 14
Diffstat (limited to '2017')
-rw-r--r--2017/input/day14.txt1
-rw-r--r--2017/src/bin/day14.rs53
2 files changed, 54 insertions, 0 deletions
diff --git a/2017/input/day14.txt b/2017/input/day14.txt
new file mode 100644
index 0000000..9d903be
--- /dev/null
+++ b/2017/input/day14.txt
@@ -0,0 +1 @@
+jzgqcdpd
\ No newline at end of file
diff --git a/2017/src/bin/day14.rs b/2017/src/bin/day14.rs
new file mode 100644
index 0000000..400a29a
--- /dev/null
+++ b/2017/src/bin/day14.rs
@@ -0,0 +1,53 @@
+use std::io::{self, Read};
+
+fn reverse(ring: &mut Vec<u32>, index: usize, len: usize) {
+    for i in 0..(len / 2) {
+        let a = (index + i) % ring.len();
+        let b = (index + len - 1 - i) % ring.len();
+        let x = ring[a];
+        ring[a] = ring[b];
+        ring[b] = x;
+    }
+}
+
+fn hash(input: &str) -> Vec<u8> {
+    let mut ring: Vec<_> = (0..256).collect();
+    let mut index = 0;
+    let mut skip = 0;
+
+    let mut lens: Vec<_> = input.as_bytes().to_vec();
+    lens.extend(&[17, 31, 73, 47, 23]);
+
+    for _ in 0..64 {
+        for len in lens.iter().cloned() {
+            reverse(&mut ring, index, len as usize);
+            index += len as usize + skip;
+            index %= ring.len();
+            skip += 1;
+        }
+    }
+
+    ring.chunks(16)
+        .map(|chunk| chunk.iter().fold(0, |a, b| a ^ b))
+        .map(|x| x as u8)
+        .collect()
+}
+
+fn solve1(input: &str) -> u32 {
+    (0..128)
+        .map(|i| hash(&format!("{}-{}", input, i)))
+        .map(|h| h.into_iter().map(u8::count_ones).sum::<u32>())
+        .sum()
+}
+
+fn main() {
+    let mut input = String::new();
+    io::stdin().read_to_string(&mut input).unwrap();
+
+    println!("Part 1: {}", solve1(input.trim()));
+}
+
+#[test]
+fn part1() {
+    assert_eq!(8108, solve1("flqrgnkx"));
+}