2023(1): Treat written digits as digits

This is wrong, though, as cases like `oneight` should return `83` whereas
I replace the `one`s first, so that `1ight` will remain that way.

See <https://www.reddit.com/r/adventofcode/comments/1884fpl/2023_day_1for_those_who_stuck_on_part_2/>.

2023/day/1/README.md

@@ -27,3 +27,28 @@ In this example, the calibration values of these four lines are `12`, `38`, `15`
 Consider your entire calibration document. _What is the sum of all of the calibration values?_
 
 To begin, [get your puzzle input](https://adventofcode.com/2023/day/1/input).
+
+Your puzzle answer was `54990`.
+
+The first half of this puzzle is complete! It provides one gold star: *
+
+## --- Part Two ---
+
+Your calculation isn't quite right. It looks like some of the digits are actually _spelled out with letters_: `one`, `two`, `three`, `four`, `five`, `six`, `seven`, `eight`, and `nine` _also_ count as valid "digits".
+
+Equipped with this new information, you now need to find the real first and last digit on each line. For example:
+
+```
+two1nine
+eightwothree
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen
+
+```
+
+In this example, the calibration values are `29`, `83`, `13`, `24`, `42`, `14`, and `76`. Adding these together produces `_281_`.
+
+_What is the sum of all of the calibration values?_

2023/day/1/main.rs

@@ -9,8 +9,32 @@ fn main() {
 	if let Ok(lines) = read_lines("./input") {
 		for line in lines {
 			if let Ok(text) = line {
-				sum = sum + first_digit(&text);
+				// TODO: Please us something like a collection instead of
-				mus = mus + last_digit(&text);
+				// hardcoding every replacement.
+				let sanitext = text
+					.replace("one",   "1")
+					.replace("two",	  "2")
+					.replace("three", "3")
+					.replace("four",  "4")
+					.replace("five",  "5")
+					.replace("six",   "6")
+					.replace("seven", "7")
+					.replace("eight", "8")
+					.replace("nine",  "9")
+					;
+				// DEBUG:
+				println!(
+					"{} => {} yields {} + {} = {}",
+					text,
+					sanitext,
+					first_digit(&sanitext),
+					last_digit(&sanitext),
+					first_digit(&sanitext) + last_digit(&sanitext)
+				);
+				sum = sum + first_digit(&sanitext);
+				mus = mus + last_digit(&sanitext);
+			} else {
+				println!("Error on line \"{:?}\"", line);
 			}
 		}
 	}