Solve day 1

src/bin/01.rs

@@ -0,0 +1,83 @@
+use itertools::assert_equal;
+
+const INPUT: &str = include_str!("../../input/01");
+const TEST_INPUT: &str = include_str!("../../input/01-test");
+const TEST_INPUT2: &str = include_str!("../../input/01-test-2");
+
+fn main() {
+    assert_eq!(part1(TEST_INPUT), 142);
+    println!("Part 1: {}", part1(INPUT));
+
+    assert_equal(replace_with_digits("eightwothree"), [8, 2, 3]);
+    assert_equal(replace_with_digits("zoneight234"), [1, 8, 2, 3, 4]);
+
+    assert_eq!(part2(TEST_INPUT2), 281);
+    println!("Part 2: {}", part2(INPUT));
+}
+
+fn part1(input: &str) -> u32 {
+    input
+        .lines()
+        .map(parse_digits)
+        .map(calibration_value_from_line)
+        .sum()
+}
+
+fn part2(input: &str) -> u32 {
+    input
+        .lines()
+        .map(replace_with_digits)
+        .map(calibration_value_from_line)
+        .sum()
+}
+
+fn calibration_value_from_line(line: Vec<u32>) -> u32 {
+    let first = line.first().copied().unwrap();
+    let last = line.last().copied().unwrap_or(first);
+    first * 10 + last
+}
+
+/// Parse all digits from the input
+fn parse_digits(line: &str) -> Vec<u32> {
+    line.chars().flat_map(|c| c.to_digit(10)).collect()
+}
+
+/// Replace all words with digits, keep digits and discard everything else.
+fn replace_with_digits(line: &str) -> Vec<u32> {
+    let replacements = [
+        ("one", 1),
+        ("two", 2),
+        ("three", 3),
+        ("four", 4),
+        ("five", 5),
+        ("six", 6),
+        ("seven", 7),
+        ("eight", 8),
+        ("nine", 9),
+    ];
+
+    let mut result = Vec::new();
+    let mut buf = line.to_string();
+
+    while !buf.is_empty() {
+        if let Some(c) = buf.chars().next() {
+            if let Some(num) = c.to_digit(10) {
+                result.push(num);
+                buf.remove(0);
+                continue;
+            }
+        }
+
+        for (find, replace) in replacements {
+            if buf.starts_with(find) {
+                result.push(replace);
+                buf.remove(0);
+                continue;
+            }
+        }
+
+        buf.remove(0);
+    }
+
+    result
+}

src/lib.rs

@@ -0,0 +1 @@
+