src/day01.rs

   1 use std::str::Lines;
   2
   3 use itertools::Itertools;
   4
   5 pub fn parse(s: &str) -> Lines {
   6     s.lines()
   7 }
   8
   9 fn calibration_value(line: &str) -> u32 {
  10     let first = line.chars().find(|c| c.is_digit(10)).unwrap();
  11     let last = line.chars().rev().find(|c| c.is_digit(10)).unwrap();
  12     format!("{}{}", first, last).parse().unwrap()
  13 }
  14
  15 pub fn calibration_sum(lines: &Lines) -> u32 {
  16     lines.clone().map(calibration_value).sum()
  17 }
  18
  19 fn calibration_value_corrected(line: &str) -> u32 {
  20     let line_chars = line.chars().collect_vec();
  21     let mut first: i32 = -1;
  22     let mut last: i32 = -1;
  23     let spelled_digits = [
  24         "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
  25     ];
  26     let mut i = 0;
  27     while i < line.len() {
  28         if let Some(d) = line_chars[i].to_digit(10) {
  29             if first == -1 {
  30                 first = d as i32;
  31             }
  32             last = d as i32;
  33         } else {
  34             for j in 0..spelled_digits.len() {
  35                 let d = spelled_digits[j];
  36                 if line[i..].starts_with(d) {
  37                     if first == -1 {
  38                         first = j as i32;
  39                     }
  40                     last = j as i32;
  41                     i += 1;
  42                     // We can't skip an entire word because of cases like
  43                     // "twone", "nineight", etc.
  44                     break;
  45                 }
  46             }
  47         }
  48
  49         i += 1;
  50     }
  51     format!("{}{}", first, last).parse().unwrap()
  52 }
  53
  54 pub fn calibration_sum_corrected(lines: &Lines) -> u32 {
  55     lines.clone().map(calibration_value_corrected).sum()
  56 }
  57
  58 #[cfg(test)]
  59 mod tests {
  60     use super::*;
  61
  62     static CALIBRATION_LINES: &str = "1abc2
  63     pqr3stu8vwx
  64     a1b2c3d4e5f
  65     treb7uchet";
  66
  67     #[test]
  68     fn part1() {
  69         let lines = parse(CALIBRATION_LINES);
  70         assert_eq!(calibration_sum(&lines), 142);
  71     }
  72
  73     static CALIBRATION_LINES_2: &str = "two1nine
  74     eightwothree
  75     abcone2threexyz
  76     xtwone3four
  77     4nineeightseven2
  78     zoneight234
  79     7pqrstsixteen";
  80
  81     #[test]
  82     fn part2() {
  83         let lines = parse(CALIBRATION_LINES_2);
  84         assert_eq!(calibration_sum_corrected(&lines), 281);
  85     }
  86 }