From c8a2ebffc4b971c28ad3e48a31077fce7af1926e Mon Sep 17 00:00:00 2001
From: YK <yk@qcl.one>
Date: Wed, 27 Nov 2024 00:05:07 +0300
Subject: [PATCH] solution: day 16

---
 src/days.rs     |  2 +-
 src/days/d16.rs | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 src/days/d16.rs

diff --git a/src/days.rs b/src/days.rs
index ec4feb9..9d545ea 100644
--- a/src/days.rs
+++ b/src/days.rs
@@ -13,7 +13,7 @@ pub mod d12;
 pub mod d13;
 pub mod d14;
 pub mod d15;
-// pub mod d16;
+pub mod d16;
 // pub mod d17;
 // pub mod d18;
 // pub mod d19;
diff --git a/src/days/d16.rs b/src/days/d16.rs
new file mode 100644
index 0000000..f7d7507
--- /dev/null
+++ b/src/days/d16.rs
@@ -0,0 +1,44 @@
+#![allow(non_upper_case_globals)]
+#![allow(unused_imports)]
+#![allow(dead_code)]
+use crate::prelude::*;
+
+pub type I = &'static str;
+pub type O = String;
+
+fn checksum (data: &str) -> String {
+    data.chars().array_chunks().map(|[a, b]| if a == b { '1' } else { '0' }).collect()
+}
+
+fn _solve (data: I, disk: usize) -> O {
+    let mut s = data.to_owned();
+    while s.len() < disk {
+        s = format!("{}0{}", &s, s.chars().rev().map(|e| if e == '1' { '0' } else { '1' }).collect::<String>());
+    }
+    s = (&s[..disk]).to_owned();
+    let mut chk = checksum(&s);
+    while chk.len() % 2 == 0 {
+        chk = checksum(&chk);
+    }
+    chk
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const input: &'static str = "01110110101001000";
+
+    #[test]
+    fn silver () {
+        let ans = _solve(input, 272);
+        assert_eq!(ans, s!("11100111011101111"))
+    }
+
+    #[test]
+    fn gold () {
+        let ans = _solve(input, 35651584);
+
+        assert_eq!(ans, s!("10001110010000110"))
+    }
+}