From fcc2250039ce0d395780d622149e944637331b86 Mon Sep 17 00:00:00 2001
From: Reiner Herrmann <reiner@reiner-h.de>
Date: Wed, 6 Dec 2023 15:39:40 +0100
Subject: day6 solution 2

---
 src/bin/day6.rs | 48 +++++++++++++++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 17 deletions(-)

(limited to 'src')

diff --git a/src/bin/day6.rs b/src/bin/day6.rs
index 3d450cb..39f7ade 100644
--- a/src/bin/day6.rs
+++ b/src/bin/day6.rs
@@ -3,34 +3,47 @@ static DAY: u8 = 6;
 fn main() {
     let input = advent::read_lines(DAY);
     println!("{DAY}a: {}", possible_ways(&input));
-    println!("{DAY}b: {}", 0);
+    println!("{DAY}b: {}", possible_ways_single_race(&input));
 }
 
-fn possible_ways(input: &[String]) -> u32 {
+fn count_ways(time: u64, record: u64) -> u64 {
+    let mut ways = 0;
+    for hold_button in 1 .. time {
+        let moving_time = time - hold_button;
+        let boat_distance = moving_time * hold_button;
+        if boat_distance > record {
+            ways += 1;
+        }
+    }
+    ways
+}
+
+fn possible_ways(input: &[String]) -> u64 {
     let get_numbers = |x: &str| {
         x.split_once(':').unwrap().1.to_string()
          .split(' ')
          .filter(|s| !s.is_empty())
          .map(|s| s.parse().unwrap())
-         .collect::<Vec<u32>>()
+         .collect::<Vec<u64>>()
     };
     let times = get_numbers(&input[0]);
     let distances = get_numbers(&input[1]);
 
-    let mut ways_list = Vec::new();
-    for (time, record) in times.iter().zip(distances.iter()) {
-        let mut ways = 0;
-        for hold_button in 1 .. *time {
-            let moving_time = time - hold_button;
-            let boat_distance = moving_time * hold_button;
-            if boat_distance > *record {
-                ways += 1;
-            }
-        }
-        ways_list.push(ways);
-    }
-    ways_list.iter()
-             .product()
+    times.iter()
+         .zip(distances.iter())
+         .map(|(time, distance)| count_ways(*time, *distance))
+         .product()
+}
+
+fn possible_ways_single_race(input: &[String]) -> u64 {
+    let get_number = |mut x: String| -> u64 {
+        x.retain(|c| c.is_ascii_digit());
+        x.parse().unwrap()
+    };
+    let time = get_number(input[0].clone());
+    let distance = get_number(input[1].clone());
+
+    count_ways(time, distance)
 }
 
 #[cfg(test)]
@@ -44,5 +57,6 @@ mod tests {
             "Distance:  9  40  200",
         ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
         assert_eq!(possible_ways(&input), 288);
+        assert_eq!(possible_ways_single_race(&input), 71503);
     }
 }
-- 
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