day(25): add initial solution

Signed-off-by: Matej Focko <me@mfocko.xyz>

samples/day25.txt

@@ -0,0 +1,13 @@
+1=-0-2
+12111
+2=0=
+21
+2=01
+111
+20012
+112
+1=-1=
+1-12
+12
+1=
+122

src/bin/day25.rs

@@ -0,0 +1,122 @@
+use std::{char::from_digit, collections::HashMap};
+
+use aoc_2022::*;
+
+type Input = Vec<String>;
+type Output = String;
+
+fn from_snafu(s: &str) -> isize {
+    (0..)
+        .zip(s.chars().rev())
+        .map(|(e, d)| {
+            5_isize.pow(e)
+                * match d {
+                    '-' => -1,
+                    '=' => -2,
+                    _ => d.to_digit(10).unwrap().try_into().unwrap(),
+                }
+        })
+        .sum()
+}
+
+fn to_snafu(mut n: isize) -> String {
+    let mut digits: Vec<char> = Vec::new();
+
+    while n > 0 {
+        let mut d = n % 5;
+        if d > 2 {
+            n += 5 - d;
+            d -= 5;
+        }
+
+        digits.push(match d {
+            -1 => '-',
+            -2 => '=',
+            _ => from_digit(d as u32, 10).unwrap(),
+        });
+
+        n /= 5;
+    }
+
+    digits.reverse();
+
+    digits.iter().join("")
+}
+
+struct Day25;
+impl Solution<Input, Output> for Day25 {
+    fn parse_input<P: AsRef<Path>>(pathname: P) -> Input {
+        file_to_lines(pathname)
+    }
+
+    fn part_1(input: &Input) -> Output {
+        to_snafu(input.iter().map(|s| from_snafu(s)).sum())
+    }
+
+    fn part_2(_input: &Input) -> Output {
+        "Merry Chrysler!!!".to_string()
+    }
+}
+
+fn main() -> Result<()> {
+    // Day25::run("sample")
+    Day25::main()
+}
+
+test_sample!(
+    day_25,
+    Day25,
+    "2=-1=0".to_string(),
+    "Merry Chrysler!!!".to_string()
+);
+
+lazy_static! {
+    static ref EXAMPLES: HashMap<isize, &'static str> = HashMap::from([
+        (1, "1"),
+        (2, "2"),
+        (3, "1="),
+        (4, "1-"),
+        (5, "10"),
+        (6, "11"),
+        (7, "12"),
+        (8, "2="),
+        (9, "2-"),
+        (10, "20"),
+        (15, "1=0"),
+        (20, "1-0"),
+        (2022, "1=11-2"),
+        (12345, "1-0---0"),
+        (314159265, "1121-1110-1=0"),
+        (1747, "1=-0-2"),
+        (906, "12111"),
+        (198, "2=0="),
+        (11, "21"),
+        (201, "2=01"),
+        (31, "111"),
+        (1257, "20012"),
+        (32, "112"),
+        (353, "1=-1="),
+        (107, "1-12"),
+        (37, "122"),
+        (4890, "2=-1=0"),
+    ]);
+}
+
+#[cfg(test)]
+mod day_25_snafu {
+    use super::*;
+
+    #[test]
+    fn test_from() {
+        for (n, s) in EXAMPLES.iter() {
+            assert_eq!(from_snafu(s), *n);
+        }
+    }
+
+    #[test]
+    fn test_to() {
+        for (n, s) in EXAMPLES.iter() {
+            assert_eq!(to_snafu(*n), s.to_string());
+        }
+    }
+}