Day 1 done

day1/.gitignore

@@ -0,0 +1 @@
+/target

day1/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "aho-corasick"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2969dcb958b36655471fc61f7e416fa76033bdd4bfed0678d8fee1e2d07a1f0"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "day1"
+version = "0.1.0"
+dependencies = [
+ "aho-corasick",
+]
+
+[[package]]
+name = "memchr"
+version = "2.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"

day1/Cargo.toml

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+[package]
+name = "day1"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+aho-corasick = "1.1.2"

day1/src/main.rs

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+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()
+}