Complete second part of 2023 day 1

2023/day1/README.md

@@ -1,5 +1,7 @@
 # Day 1: Trebuchet?!
 
+## Part 1
+
 Something is wrong with global snow production, and you've been selected to take a look. 
 The Elves have even given you a map; on it, they've used stars to mark the top fifty 
 locations that are likely to be having problems.
@@ -40,3 +42,24 @@ In this example, the calibration values of these four lines are 12, 38, 15, and
 Adding these together produces 142.
 
 Consider your entire calibration document. **What is the sum of all of the calibration values?**
+
+## Part 2
+
+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/day1/src/main.rs

@@ -1,24 +1,78 @@
 use std::collections::VecDeque;
-
-fn get_lines(raw: &str) -> Vec<Vec<char>> {
-    raw.split('\n').map(|line| line.chars().collect()).collect()
+fn word_to_digit(s: &str) -> char {
+    match s {
+        "one" | "1" => '1',
+        "two" | "2" => '2',
+        "three" | "3" => '3',
+        "four" | "4" => '4',
+        "five" | "5" => '5',
+        "six" | "6" => '6',
+        "seven" | "7" => '7',
+        "eight" | "8" => '8',
+        "nine" | "9" => '9',
+        _ => '0',
+    }
 }
 
-fn filter_lines(raw: &Vec<Vec<char>>) -> Vec<VecDeque<char>> {
-    raw.iter()
-        .map(|line| {
-            let line: Vec<char> = line
-                .into_iter()
-                .filter(|c| c.is_digit(10))
-                .map(|c| c.to_owned())
+fn line_to_digits(line: &str) -> VecDeque<char> {
+    let numbers = Vec::from([
+        "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "1", "2", "3", "4",
+        "5", "6", "7", "8", "9", "0",
+    ]);
+
+    let mut digits: VecDeque<char> = VecDeque::new();
+
+    // Find the numbers/number words in the line
+    let first_matches: Vec<(usize, &str)> = numbers
+        .iter()
+        .map(|search| line.match_indices(*search).collect::<Vec<(usize, &str)>>())
+        .filter(|search| search.len() > 0)
+        .map(|search| search[0])
         .collect();
-            VecDeque::from(line)
+
+    let last_matches: Vec<(usize, &str)> = numbers
+        .iter()
+        .map(|search| line.rmatch_indices(*search).collect::<Vec<(usize, &str)>>())
+        .filter(|search| search.len() > 0)
+        .map(|search| search[0])
+        .collect();
+
+    // Find the matches of the string in order,
+    // and return the cleaned up matches
+    for min in 0..line.len() {
+        if let Some(m) = first_matches.iter().find(|m| m.0 == min) {
+            digits.push_back(word_to_digit(m.1));
+            break;
+        }
+    }
+
+    for max in (0..line.len()).rev() {
+        if let Some(m) = last_matches.iter().find(|m| m.0 == max) {
+            digits.push_back(word_to_digit(m.1));
+            break;
+        }
+    }
+
+    digits
+}
+
+fn get_lines(raw: &str, words: bool) -> Vec<VecDeque<char>> {
+    raw.split('\n')
+        .map(|line| {
+            if words {
+                line_to_digits(line)
+            } else {
+                line.chars()
+                    .filter(|c| c.is_digit(10))
+                    .collect::<VecDeque<char>>()
+            }
         })
         .collect()
 }
 
 fn get_values(raw: &mut Vec<VecDeque<char>>) -> Vec<usize> {
     raw.iter_mut()
+        .filter(|line| line.len() > 0)
         .map(|line| {
             let first = match line.pop_front() {
                 Some(c) => c,
@@ -41,9 +95,37 @@ fn sum(raw: Vec<usize>) -> usize {
 
 fn main() {
     let file_str = include_str!("input.txt");
-    let lines = get_lines(file_str);
-    let mut lines = filter_lines(&lines);
+    let mut lines = get_lines(file_str, false);
     let values = get_values(&mut lines);
 
-    println!("Total: {}", sum(values));
+    println!("Part 1 Total: {}", sum(values));
+
+    let mut lines = get_lines(file_str, true);
+    let values = get_values(&mut lines);
+
+    println!("Part 2 Total: {}", sum(values));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_first_result() {
+        let file_str = include_str!("input.txt");
+        let mut lines = get_lines(file_str, false);
+        let values = get_values(&mut lines);
+
+        assert_eq!(sum(values), 54990);
+    }
+
+    #[test]
+    fn test_second_example_values() {
+        let example = "two1nine\neightwothree\nabcone2threexyz\nxtwone3four\n4nineeightseven2\nzoneight234\n7pqrstsixteen";
+        let mut lines = get_lines(example, true);
+        let values = get_values(&mut lines);
+
+        assert_eq!(values, Vec::from([29, 83, 13, 24, 42, 14, 76]));
+        assert_eq!(sum(values), 281);
+    }
 }