day 6

aoc_puzzle_cache/day_6

@@ -0,0 +1,2 @@
+Time:        53     91     67     68
+Distance:   250   1330   1081   1025

src/bin/day5.rs

@@ -176,6 +176,7 @@ fn part2(input: String) -> Result<usize> {
         .map(|s| s.parse::<usize>().expect("failed to parse seed as number"))
         .tuples()
         .flat_map(|(start, length)| start..start + length)
+        .take(3000)
         // Squeeze with rayon for brute force approach
         .par_bridge()
         .map(|source| almanac.map_source(source, "seed", "location"))

src/bin/day6.rs

@@ -7,41 +7,66 @@ use std::{str::FromStr, time::Instant};
 static DAY: u8 = 6;
 
 #[derive(Debug, Builder, Clone)]
-struct Todo {}
+struct Race {
+    time: usize,
+    record_distance: usize,
+}
 
-impl FromStr for Todo {
-    type Err = BoxE;
+impl Race {
+    fn get_roots(&self) -> (usize, usize) {
+        let a = -1.0;
+        let b = self.time as f64;
+        let c = -(self.record_distance as f64);
+        let n1 = (-b + f64::sqrt(b * b - (4.0 * a * c))) / (2.0 * a);
+        let n2 = (-b - f64::sqrt(b * b - (4.0 * a * c))) / (2.0 * a);
+        if n1 < n2 {
+            // floor and round up to ensure we win
+            let n1 = f64::floor(n1) as usize + 1;
 
-    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
-        let mut builder = TodoBuilder::default();
-        Ok(builder.build()?)
+            // ceil and round down to ensure we don't exceed time cap
+            let n2 = f64::ceil(n2) as usize - 1;
+            (n1, n2)
+        } else {
+            let n1 = f64::ceil(n1) as usize - 1;
+            let n2 = f64::floor(n2) as usize + 1;
+            (n2, n1)
         }
     }
 
-fn part1(input: String) -> Result<usize> {
-    // parse
-    let start = Instant::now();
-    let todo: Todo = input.parse()?;
-    let parsed_time = start.elapsed();
+    fn get_ways_to_beat_count(&self) -> usize {
+        let (n1, n2) = self.get_roots();
+        if self.time < n1 {
+            0
+        } else {
+            let n2 = usize::min(self.time, n2);
+            n2 - n1 + 1
+        }
+    }
+}
 
+fn part1(races: &[Race]) -> Result<usize> {
     // algo
     let start = Instant::now();
-    let answer = 0;
+    let mut answer = 1;
+    for race in races {
+        let ways_to_beat = race.get_ways_to_beat_count();
+        println!(
+            "Race: {:?}, roots: {:?}, ways to beat: {:?}",
+            race,
+            race.get_roots(),
+            race.get_ways_to_beat_count()
+        );
+        answer *= ways_to_beat;
+    }
     let algo_time = start.elapsed();
 
     // output
     println!("part 1: {answer}");
-    println!("\tparse: {parsed_time:?}");
     println!("\talgo: {algo_time:?}");
     Ok(answer)
 }
 
-fn part2(input: String) -> Result<usize> {
-    // parse
-    let start = Instant::now();
-    let todo: Todo = input.parse()?;
-    let parsed_time = start.elapsed();
-
+fn part2(races: &[Race]) -> Result<usize> {
     // algo
     let start = Instant::now();
     let answer = 0;
@@ -49,18 +74,57 @@ fn part2(input: String) -> Result<usize> {
 
     // output
     println!("part 2: {answer}");
-    println!("\tparse: {parsed_time:?}");
     println!("\talgo: {algo_time:?}");
     Ok(answer)
 }
 
 #[tokio::main]
 async fn main() -> Result<()> {
-    let input = utils::aoc::get_puzzle_input(DAY).await?;
+    // let input = utils::aoc::get_puzzle_input(DAY).await?;
     println!("Day {DAY}");
     println!("=====");
-    part1(input.clone())?;
-    part2(input.clone())?;
+    let races: [Race; 4] = [
+        Race {
+            time: 53,
+            record_distance: 250,
+        },
+        Race {
+            time: 91,
+            record_distance: 1330,
+        },
+        Race {
+            time: 67,
+            record_distance: 1081,
+        },
+        Race {
+            time: 68,
+            record_distance: 1025,
+        },
+    ];
+    let races: [Race; 1] = [Race {
+        time: 53916768,
+        record_distance: 250133010811025,
+    }];
+    let races: [Race; 3] = [
+        Race {
+            time: 7,
+            record_distance: 9,
+        },
+        Race {
+            time: 15,
+            record_distance: 40,
+        },
+        Race {
+            time: 30,
+            record_distance: 200,
+        },
+    ];
+    let races: [Race; 1] = [Race {
+        time: 71530,
+        record_distance: 940200,
+    }];
+    part1(&races)?;
+    part2(&races)?;
     Ok(())
 }
 
@@ -68,17 +132,30 @@ async fn main() -> Result<()> {
 mod tests {
     use super::*;
 
-    static DATA: &'static str = "TODO_REPLACE";
+    static RACES: [Race; 3] = [
+        Race {
+            time: 7,
+            record_distance: 9,
+        },
+        Race {
+            time: 15,
+            record_distance: 40,
+        },
+        Race {
+            time: 30,
+            record_distance: 200,
+        },
+    ];
 
     #[test]
     fn test_part_1() -> Result<()> {
-        assert_eq!(part1(DATA.to_owned())?, 0);
+        assert_eq!(part1(&RACES)?, 288);
         Ok(())
     }
 
     #[test]
     fn test_part_2() -> Result<()> {
-        assert_eq!(part2(DATA.to_owned())?, 0);
+        assert_eq!(part2(&RACES)?, 0);
         Ok(())
     }
 }