From 00000130fa2839845c36a05856ea045cee539a62 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matej=20Jane=C5=BEi=C4=8D?= <janezic.mj@gmail.com>
Date: Wed, 6 Dec 2023 07:06:16 +0100
Subject: [PATCH] solution: day 6

---
 data/examples/06.txt |  2 ++
 src/bin/06.rs        | 63 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 data/examples/06.txt
 create mode 100644 src/bin/06.rs

diff --git a/data/examples/06.txt b/data/examples/06.txt
new file mode 100644
index 000000000..28f5ae9
--- /dev/null
+++ b/data/examples/06.txt
@@ -0,0 +1,2 @@
+Time:      7  15   30
+Distance:  9  40  200
diff --git a/src/bin/06.rs b/src/bin/06.rs
new file mode 100644
index 000000000..f4be2cb
--- /dev/null
+++ b/src/bin/06.rs
@@ -0,0 +1,63 @@
+use aoc::parsers::to_vec;
+
+fn win_options((time, distance): (u64, u64)) -> u64 {
+    let discriminant = ((time.pow(2) - 4 * distance) as f64).sqrt();
+
+    let first_zero = (time as f64 - discriminant) / 2.0;
+    let mut second_zero = (time as f64 + discriminant) / 2.0;
+
+    if second_zero.fract() == 0.0 {
+        second_zero -= 1.0
+    }
+
+    second_zero as u64 - first_zero as u64
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let (upt, upd) = input.split_once('\n')?;
+    let time: Vec<u64> = to_vec(upt.strip_prefix("Time:      ")?, ' ');
+    let distance: Vec<u64> = to_vec(upd.strip_prefix("Distance:  ")?, ' ');
+
+    Some(time.into_iter().zip(distance).map(win_options).product())
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let (upt, upd) = input.split_once('\n')?;
+    let time: u64 = upt
+        .strip_prefix("Time:      ")?
+        .split(' ')
+        .flat_map(|x| x.chars())
+        .collect::<String>()
+        .parse()
+        .ok()?;
+    let distance: u64 = upd
+        .strip_prefix("Distance:  ")?
+        .split(' ')
+        .flat_map(|x| x.chars())
+        .collect::<String>()
+        .parse()
+        .ok()?;
+
+    Some(win_options((time, distance)))
+}
+
+aoc::solution!(6);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        assert_eq!(
+            part_one(&aoc::template::read_file("examples", 6)),
+            Some(288)
+        );
+    }
+    #[test]
+    fn test_part_two() {
+        assert_eq!(
+            part_two(&aoc::template::read_file("examples", 6)),
+            Some(71503)
+        );
+    }
+}