add day 6

advent2023/src/bin/day06/main.rs

@@ -0,0 +1,80 @@
+fn parse_line_part1<'a>(iter: &mut impl Iterator<Item = &'a str>) -> Vec<u64> {
+    iter.next()
+        .unwrap()
+        .split_whitespace()
+        .skip(1)
+        .map(|s| s.parse().unwrap())
+        .collect()
+}
+
+fn parse_part1(input: &str) -> (Vec<u64>, Vec<u64>) {
+    let mut iter = input.lines();
+    let times = parse_line_part1(&mut iter);
+    let distances = parse_line_part1(&mut iter);
+    (times, distances)
+}
+
+fn ways2win(total_time: u64, distance: u64) -> u64 {
+    let is_way_to_win = |hold_time| hold_time * (total_time - hold_time) > distance;
+    let min = (1..total_time)
+        .find(|&hold_time| is_way_to_win(hold_time))
+        .unwrap();
+    let max = (1..total_time)
+        .rfind(|&hold_time| is_way_to_win(hold_time))
+        .unwrap();
+    max + 1 - min
+}
+
+fn part1(input: &str) -> u64 {
+    let (times, distances) = parse_part1(input);
+    times
+        .into_iter()
+        .zip(distances)
+        .map(|(time, distance)| ways2win(time, distance))
+        .product()
+}
+
+fn parse_line_part2<'a>(iter: &mut impl Iterator<Item = &'a str>) -> u64 {
+    iter.next()
+        .unwrap()
+        .split_once(':')
+        .unwrap()
+        .1
+        .replace(char::is_whitespace, "")
+        .parse()
+        .unwrap()
+}
+
+fn parse_part2(input: &str) -> (u64, u64) {
+    let mut iter = input.lines();
+    let time = parse_line_part2(&mut iter);
+    let distance = parse_line_part2(&mut iter);
+    (time, distance)
+}
+
+fn part2(input: &str) -> u64 {
+    let (time, distance) = parse_part2(input);
+    ways2win(time, distance)
+}
+
+fn main() {
+    let file_contents = vec![include_str!("example"), include_str!("input")];
+    advent2023::calculate_and_print(&file_contents, part1, part2);
+}
+
+#[cfg(test)]
+mod day06 {
+    use super::*;
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(include_str!("example")), 288);
+        assert_eq!(part1(include_str!("input")), 4403592);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(include_str!("example")), 71503);
+        assert_eq!(part2(include_str!("input")), 38017587);
+    }
+}