Day 1 done

day1/src/main.rs

@@ -0,0 +1,49 @@
+use aho_corasick::AhoCorasick;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+fn main() {
+    let input = read_input();
+    let part_1_result = part_1(&input);
+    let part_2_result = part_2(&input);
+    println!("Part 1: {part_1_result}");
+    println!("Part 2: {part_2_result}");
+}
+
+fn read_input() -> Vec<String> {
+    BufReader::new(File::open("input").expect("open input"))
+        .lines()
+        .map(|line| line.expect("line"))
+        .collect()
+}
+
+fn part_1(input: &[String]) -> u32 {
+    input
+        .iter()
+        .map(|line| {
+            let digits: Vec<_> = line.chars().filter_map(|chr| chr.to_digit(10)).collect();
+            digits[0] * 10 + digits.last().unwrap()
+        })
+        .sum()
+}
+
+fn part_2(input: &[String]) -> u32 {
+    let patterns = &[
+        "one", "1", "two", "2", "three", "3", "four", "4", "five", "5", "six", "6", "seven", "7",
+        "eight", "8", "nine", "9",
+    ];
+    let ac = AhoCorasick::new(patterns).unwrap();
+    input
+        .iter()
+        .map(|line| {
+            let mut matches = ac.find_overlapping_iter(line);
+            let first = matches.next().expect("first match").pattern().as_u32() / 2 + 1;
+            let last = if let Some(last) = matches.last() {
+                last.pattern().as_u32() / 2 + 1
+            } else {
+                first
+            };
+            first * 10 + last
+        })
+        .sum()
+}