day 1 in the books

data/examples/01.txt

@@ -0,0 +1,10 @@
+1abc2
+pqr3stu8vwx
+a1b2c3d4e5f
+treb7uchet
+two1nine
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen

src/bin/01.rs

@@ -0,0 +1,80 @@
+advent_of_code::solution!(1);
+
+pub fn part_one(input: &str) -> Option<u32> {
+    Some(
+        input
+            .lines()
+            .map(|line| {
+                let mut digits = line.char_indices().filter_map(|c| c.1.to_digit(10));
+                let first = digits.next().expect("Expected a digit");
+                let last = if let Some(last) = digits.last() {
+                    last
+                } else {
+                    first
+                };
+                first * 10 + last
+            })
+            .sum(),
+    )
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    Some(
+        input
+            .lines()
+            .map(|line| {
+                let mut digits = line.char_indices().filter_map(|c| {
+                    if let Some(digit) = c.1.to_digit(10) {
+                        Some(digit)
+                    } else {
+                        if line[c.0..].starts_with("one") {
+                            Some(1)
+                        } else if line[c.0..].starts_with("two") {
+                            Some(2)
+                        } else if line[c.0..].starts_with("three") {
+                            Some(3)
+                        } else if line[c.0..].starts_with("four") {
+                            Some(4)
+                        } else if line[c.0..].starts_with("five") {
+                            Some(5)
+                        } else if line[c.0..].starts_with("six") {
+                            Some(6)
+                        } else if line[c.0..].starts_with("seven") {
+                            Some(7)
+                        } else if line[c.0..].starts_with("eight") {
+                            Some(8)
+                        } else if line[c.0..].starts_with("nine") {
+                            Some(9)
+                        } else {
+                            None
+                        }
+                    }
+                });
+                let first = digits.next().expect("Expected a digit");
+                let last = if let Some(last) = digits.last() {
+                    last
+                } else {
+                    first
+                };
+                first * 10 + last
+            })
+            .sum(),
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(142 + 209));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(142 + 198));
+    }
+}