diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/day25.rs | 73 | ||||
| -rw-r--r-- | src/main.rs | 6 |
2 files changed, 77 insertions, 2 deletions
diff --git a/src/day25.rs b/src/day25.rs new file mode 100644 index 0000000..2d26028 --- /dev/null +++ b/src/day25.rs @@ -0,0 +1,73 @@ +fn from_snafu(s: &str) -> i64 { + // This is the easy bit... + let mut i: i64 = 0; + let mut pow: i64 = 1; + for ch in s.chars().rev() { + match ch { + '2' => i += 2 * pow, + '1' => i += 1 * pow, + '0' => {}, // additive identity! + '-' => i += -1 * pow, + '=' => i += -2 * pow, + _ => panic!("unexpected input {}", ch) + } + pow *= 5; + } + i +} + +#[cfg(test)] +mod tests { + use super::*; + #[test] + fn test_from_snafu() { + let cases = vec![ + ("1=-0-2", "1747"), + ( "12111", "906"), + ( "2=0=", "198"), + ( "21", "11"), // works + ( "2=01", "201"), // 201,1 > 40,0 > 8,= > 1,1 + ( "111", "31"), // works + ( "20012", "1257"), //works + ( "112", "32"), // works + ( "1=-1=", "353"), // broke + ( "1-12", "107"), + ( "12", "7"), + ( "1=", "3"), + ( "122", "37"), + ]; + for (snafu, decimal) in cases { + let x = from_snafu(snafu); + assert_eq!(x.to_string().as_str(), decimal); + assert_eq!(to_snafu(x), snafu); + } + } +} + +fn to_snafu(mut i: i64) -> String { + // how to do this :thinking: add two, mod 5,take away 2? // nope + let mut res = Vec::<char>::new(); + while i != 0 { + let d = ((i + 2) % 5) - 2; + let ch = match d { + 2 => '2', + 1 => '1', + 0 => '0', + -1 => '-', + -2 => '=', + _ => panic!("unexpected digit {}", d) + }; + res.push(ch); + i = (i + 2) / 5; + } + res.reverse(); + res.into_iter().collect::<String>() + +} + +pub fn run(input: String) { + let s: i64 = input.lines() + .map(from_snafu) + .sum(); + println!("Day 25: {}", to_snafu(s)); +}
\ No newline at end of file diff --git a/src/main.rs b/src/main.rs index e865636..886b86c 100644 --- a/src/main.rs +++ b/src/main.rs @@ -20,7 +20,8 @@ use std::fs; // mod day15; // mod day16; //mod day17; -mod day18; +//mod day18; +mod day25; fn main() { // day1::run(fs::read_to_string("input/day1.txt").expect("Failed to read input file!")); @@ -40,5 +41,6 @@ fn main() { // day15::run(fs::read_to_string("input/day15.txt").expect("Failed to read input file!")); // day16::run(fs::read_to_string("input/day16.txt").expect("Failed to read input file!")); //day17::run(fs::read_to_string("input/day17.txt").expect("Failed to read input file!")); - day18::run(fs::read_to_string("input/day18.txt").expect("Failed to read input file!")); + //day18::run(fs::read_to_string("input/day18.txt").expect("Failed to read input file!")); + day25::run(fs::read_to_string("input/day25.txt").expect("Failed to read input file!")); } |