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static DAY: u8 = 1;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", sum_digits(&input, false));
println!("{DAY}b: {}", sum_digits(&input, true));
}
fn starts_with_number(word: &str, consider_words: bool) -> Option<u32> {
if let Some(digit) = word.chars().next().unwrap().to_digit(10) {
return Some(digit);
}
if !consider_words {
return None
}
let digits = ["one", "two", "three", "four", "five", "six", "seven", "eight", "nine"];
for (pos, digit) in digits.iter().enumerate() {
if word.starts_with(digit) {
return Some(pos as u32 + 1);
}
}
None
}
fn sum_digits(input: &[String], consider_words: bool) -> u32 {
let mut sum = 0;
for line in input {
let mut line_number = 0;
for pos in 0 .. line.len() {
if let Some(number) = starts_with_number(&line[pos..], consider_words) {
line_number += 10 * number;
break;
}
}
for pos in (0 .. line.len()).rev() {
if let Some(number) = starts_with_number(&line[pos..], consider_words) {
line_number += number;
break;
}
}
sum += line_number;
}
sum
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"1abc2",
"pqr3stu8vwx",
"a1b2c3d4e5f",
"treb7uchet",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(sum_digits(&input, false), 142);
let input = [
"two1nine",
"eightwothree",
"abcone2threexyz",
"xtwone3four",
"4nineeightseven2",
"zoneight234",
"7pqrstsixteen",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(sum_digits(&input, true), 281);
}
}
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