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|
static DAY: u8 = 25;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", console_number(&input));
}
fn snafu_to_number(input: &str) -> i64 {
let mut number = 0;
for c in input.chars() {
number *= 5;
number += match c {
'0' => 0,
'1' => 1,
'2' => 2,
'-' => -1,
'=' => -2,
_ => unimplemented!(),
};
}
number
}
fn number_to_snafu(input: i64) -> String {
let mut number = input;
let mut digits = Vec::new();
while number > 0 {
digits.push(number % 5);
number /= 5;
}
digits.push(0);
for i in 0 .. digits.len() - 1 {
if digits[i] == 3 {
digits[i+1] += 1;
digits[i] = -2;
} else if digits[i] == 4 {
digits[i+1] += 1;
digits[i] = -1;
} else if digits[i] == 5 {
digits[i+1] += 1;
digits[i] = 0;
}
}
let mut snafu = String::new();
for digit in digits.iter().rev().skip_while(|&x| *x == 0) {
match digit {
-1 => snafu.push('-'),
-2 => snafu.push('='),
0 => snafu.push('0'),
1 => snafu.push('1'),
2 => snafu.push('2'),
_ => unimplemented!(),
}
}
snafu
}
fn console_number(input: &[String]) -> String {
let number = input.iter()
.map(|x| snafu_to_number(x))
.sum();
number_to_snafu(number)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"1=-0-2",
"12111",
"2=0=",
"21",
"2=01",
"111",
"20012",
"112",
"1=-1=",
"1-12",
"12",
"1=",
"122",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(console_number(&input), "2=-1=0");
}
#[test]
fn test_number_to_snafu() {
assert_eq!(number_to_snafu(1), "1");
assert_eq!(number_to_snafu(2), "2");
assert_eq!(number_to_snafu(3), "1=");
assert_eq!(number_to_snafu(4), "1-");
assert_eq!(number_to_snafu(5), "10");
assert_eq!(number_to_snafu(6), "11");
assert_eq!(number_to_snafu(7), "12");
assert_eq!(number_to_snafu(8), "2=");
assert_eq!(number_to_snafu(9), "2-");
assert_eq!(number_to_snafu(10), "20");
assert_eq!(number_to_snafu(15), "1=0");
assert_eq!(number_to_snafu(20), "1-0");
assert_eq!(number_to_snafu(2022), "1=11-2");
assert_eq!(number_to_snafu(12345), "1-0---0");
assert_eq!(number_to_snafu(314159265), "1121-1110-1=0");
}
}
|
