Day1

src/day1.rs

@@ -0,0 +1,114 @@
+use core::num;
+
+use crate::util::{Day, Solution};
+
+pub struct Day1;
+
+impl Day for Day1 {
+    fn solve(input: &str) -> Solution {
+        let (part1, part2) = input
+            .lines()
+            .take_while(|line| !line.is_empty())
+            .map(|line| (part1_line(&line), part2_line(line)))
+            .reduce(|(p1, p2), (part1, part2)| (p1 + part1, p2 + part2))
+            .expect("Failed to solve");
+
+        (part1, part2)
+    }
+}
+
+fn part1_line(line: &str) -> usize {
+    let numbers: Vec<usize> = line
+        .chars()
+        .filter(|char| char.is_ascii_digit())
+        .map(|char| char.to_string().parse().expect("Expected a number"))
+        .collect();
+    let first = numbers.first().unwrap_or(&0);
+    let last = numbers.last().unwrap_or(&0);
+    first * 10 + last
+}
+
+fn part2_line(line: &str) -> usize {
+    const WORD_NUMBERS: [&str; 9] = [
+        "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
+    ];
+
+    fn of_two_option<F>(a: Option<usize>, b: Option<usize>, f: F) -> Option<usize>
+    where
+        F: Fn(usize, usize) -> usize,
+    {
+        match (a, b) {
+            (None, None) => None,
+            (None, Some(i)) => Some(i),
+            (Some(i), None) => Some(i),
+            (Some(l), Some(r)) => Some(f(l, r)),
+        }
+    }
+
+    let res = WORD_NUMBERS
+        .iter()
+        .enumerate()
+        .flat_map(|(index, &word)| {
+            let number = index + 1;
+            let (number_first, number_last) = {
+                let number_string = &number.to_string();
+                (line.find(number_string), line.rfind(number_string))
+            };
+            let word_first = line.find(word);
+            let word_last = line.rfind(word);
+
+            let min = of_two_option(number_first, word_first, usize::min).map(|idx| (idx, number));
+            let max = of_two_option(number_last, word_last, usize::max).map(|idx| (idx, number));
+            vec![min, max]
+        })
+        .flatten()
+        .collect::<Vec<_>>();
+
+    let tens = res
+        .iter()
+        .min_by_key(|(idx, _num)| idx)
+        .map(|(_, number)| number)
+        .expect("Expected to find at least one number");
+    let ones = res
+        .iter()
+        .max_by_key(|(idx, _num)| idx)
+        .map(|(_, number)| number)
+        .expect("Expected to find at least one number");
+
+    println!("In {line} we have ({tens}, {ones})");
+
+    // 55336 too HIGH
+    10 * tens + ones
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::util::Day;
+
+    use super::Day1;
+
+    const EXAMPLE1: &str = "\
+    1abc2\n\
+    pqr3stu8vwx\n\
+    a1b2c3d4e5f\n\
+    treb7uchet";
+
+    const EXAMPLE2: &str = "\
+    two1nine\n\
+    eightwothree\n\
+    abcone2threexyz\n\
+    xtwone3four\n\
+    4nineeightseven2\n\
+    zoneight234\n\
+    7pqrstsixteen";
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(142, Day1::solve(EXAMPLE1).0);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(281, Day1::solve(EXAMPLE2).1);
+    }
+}

src/main.rs

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+use day1::Day1;
+use util::{read_input, Day};
+
+mod day1;
+mod util;
+
+fn main() {
+    let day1 = solve(1);
+    println!("Day1 = {day1:?}");
+}
+
+fn solve(day: u8) -> (usize, usize) {
+    let input = &read_input(day).unwrap();
+    match day {
+        1 => Day1::solve(input),
+        _ if day > 25 => unreachable!("There are only 25 days!"),
+        _ => todo!("Not done!"),
+    }
+}