Day 6

src/day6/mod.rs

@@ -0,0 +1,78 @@
+use super::Part;
+use log::{debug, info, trace};
+use regex::Regex;
+
+fn solve_race(d: u64, t: u64) -> u64 {
+    info!("Resolving race d={}, t={}", d, t);
+    let mut count = 0;
+
+    for x in 0..t { //TODO: we could definetly do maths (erk) here but i'm in a rush
+        trace!("If I am holding {}ms the boat will travel {}mm/{}mm ", x, (t-x)*x, d);
+        if (t-x)*x > d { 
+            trace!("Found a solution: x={}:  {} * {} = {}", x, x, t-x, d);
+            count+=1;
+        }
+    }
+
+    count
+}
+
+pub fn solve(lines: Vec<String>, part: Part) -> u64 {
+    let mut time_line = lines.get(0).unwrap().to_owned();
+    let mut distance_line = lines.get(1).unwrap().to_owned();
+
+    if let Part::Two = part {
+        time_line.remove_matches(' ');
+        distance_line.remove_matches(' ');
+    }
+
+    let re = Regex::new(r"\d+").unwrap();
+
+    let times : Vec<u64> = re.captures_iter(&time_line)
+        .map(|capture| capture.get(0).unwrap().as_str().parse().unwrap())
+        .collect();
+    debug!("Current times: {:?}", times);
+
+    let distances : Vec<u64> = re.captures_iter(&distance_line)
+        .map(|capture| capture.get(0).unwrap().as_str().parse().unwrap())
+        .collect();
+    debug!("Current distances: {:?}", distances);
+
+    assert_eq!(times.len(), distances.len());
+
+    // Holding 1 ms => +1 mm/ms
+    // T: total time
+    // d: distance
+    // x: number of seconds holding the button
+    // x * (T - x) = d
+    // Tx - x² = d
+
+    let mut result = 1;
+    for n in 0..(times.len()) {
+        let t = times[n];
+        let d = distances[n];
+
+        result *= solve_race(d, t);
+    }
+
+    result
+}
+
+#[cfg(test)]
+mod tests {
+    use log::info;
+
+    use crate::{day6::solve_race, utils::init_logger_test};
+    fn init(){
+        init_logger_test();
+    }
+
+    #[test]
+    fn test_solve_race() {
+        init();
+
+        assert_eq!(solve_race(9, 7), 4);
+        assert_eq!(solve_race(40, 15), 8);
+        assert_eq!(solve_race(200, 30), 9);
+    }
+}

src/main.rs

@@ -1,10 +1,12 @@
 #![feature(let_chains)]
+#![feature(string_remove_matches)]
 
 mod day1;
 mod day2;
 mod day3;
 mod day4;
 mod day5;
+mod day6;
 mod utils;
 use log::info;
 use utils::Part;
@@ -18,13 +20,8 @@ fn main() {
         .format_timestamp(None)
         .init();
 
-    let data = utils::lines_from_file("./datasets/adventofcode.com_2023_day_5_input.txt").expect("Can't load the data");
+    let data = utils::lines_from_file("./datasets/adventofcode.com_2023_day_6_input.txt").expect("Can't load the data");
     //let data = utils::lines_from_file("./datasets/test.txt").expect("Can't load the data");
-    let result = day5::solve(data.clone(), Part::One);
-    let result2 = day5::solve(data, Part::Two);
-
-    info!("Result part 1: {}", result);
-    info!("Result part 2: {}", result2);
 }
 
 
@@ -71,4 +68,13 @@ mod tests {
         assert_eq!(result, 20407);
         assert_eq!(result2, 23806951);
     }
+
+    #[test] 
+    fn day6() {
+        let data_path = "./datasets/adventofcode.com_2023_day_6_input.txt"; 
+        let result = day6::solve(utils::lines_from_file(data_path).expect("Could not load the dataset for day 3"), Part::One);
+        let result2 = day6::solve(utils::lines_from_file(data_path).expect("Could not load the dataset for day 3"), Part::Two);
+        assert_eq!(result, 2612736);
+        assert_eq!(result2, 29891250);
+    }
 }

src/utils.rs

@@ -14,4 +14,12 @@ pub fn lines_from_file(filename: impl AsRef<Path>) -> Result<Vec<String>> {
 pub enum Part {
     One, 
     Two
+}
+
+pub fn init_logger_test() {
+    env_logger::builder()
+        .filter_level(log::LevelFilter::Debug)
+        .format_timestamp(None)
+        .is_test(true)
+        .init();
 }