Day 1

.gitignore

@@ -12,3 +12,10 @@ Cargo.lock
 
 # MSVC Windows builds of rustc generate these, which store debugging information
 *.pdb
+
+# Added by cargo
+
+/target
+
+# Don't commit my personal input.txt files
+input.txt

Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "advent-of-code-2023"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0"
+phf = { version = "0.11", features = ["macros"] }

src/day01/input/test1.txt

@@ -0,0 +1,4 @@
+1abc2
+pqr3stu8vwx
+a1b2c3d4e5f
+treb7uchet

src/day01/input/test2.txt

@@ -0,0 +1,7 @@
+two1nine
+eightwothree
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen

src/day01/mod.rs

@@ -0,0 +1,107 @@
+use std::cmp::min;
+
+use anyhow::{anyhow, Result};
+use phf::phf_map;
+
+use crate::instrument::instrument;
+
+const INPUT: &str = include_str!("input/input.txt");
+static DIGITS: phf::Map<&[u8], u8> = phf_map! {
+    b"zero" => 0,
+    b"one" => 1,
+    b"two" => 2,
+    b"three" => 3,
+    b"four" => 4,
+    b"five" => 5,
+    b"six" => 6,
+    b"seven" => 7,
+    b"eight" => 8,
+    b"nine" => 9,
+    b"0" => 0,
+    b"1" => 1,
+    b"2" => 2,
+    b"3" => 3,
+    b"4" => 4,
+    b"5" => 5,
+    b"6" => 6,
+    b"7" => 7,
+    b"8" => 8,
+    b"9" => 9,
+};
+
+fn find_num(line: &[u8], reverse: bool) -> Option<u8> {
+    let window_size = min(line.len(), 5);
+    for i in 0..line.len() {
+        for j in 1..min(window_size + 1, line.len() - i + 1) {
+            if j == 2 {
+                continue; // no two-byte digits
+            }
+            if !reverse {
+                if let Some(digit) = DIGITS.get(&line[i..i + j]) {
+                    return Some(*digit);
+                }
+            } else if let Some(digit) = DIGITS.get(&line[line.len() - i - j..line.len() - i]) {
+                return Some(*digit);
+            }
+        }
+    }
+    None
+}
+
+fn part1(input: &str) -> Result<u32> {
+    let mut sum: u32 = 0;
+    for line in input.trim().split('\n') {
+        let first = line
+            .as_bytes()
+            .iter()
+            .find(|c| c.is_ascii_digit())
+            .map(|c| c - b'0')
+            .ok_or_else(|| anyhow!("Invalid input: no digits found in line {}", line))?;
+        let last = line
+            .as_bytes()
+            .iter()
+            .rev()
+            .find(|c| c.is_ascii_digit())
+            .map(|c| c - b'0')
+            .ok_or_else(|| anyhow!("Invalid input: no digits found in line {}", line))?;
+        sum += (first as u32 * 10) + last as u32;
+    }
+    Ok(sum)
+}
+
+fn part2(input: &str) -> Result<u32> {
+    let mut sum = 0;
+    for line in input.trim().split('\n') {
+        let first = find_num(line.as_bytes(), false)
+            .ok_or_else(|| anyhow!("Invalid input: no digits found in line {}", line))?;
+        let last = find_num(line.as_bytes(), true)
+            .ok_or_else(|| anyhow!("Invalid input: no digits found in line {}", line))?;
+        sum += (first as u32 * 10) + last as u32;
+    }
+    Ok(sum)
+}
+
+pub fn solve() -> Result<()> {
+    println!("Day 01");
+    instrument!(part1(INPUT)?, part2(INPUT)?);
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_INPUT1: &str = include_str!("input/test1.txt");
+    const TEST_INPUT2: &str = include_str!("input/test2.txt");
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(TEST_INPUT1).unwrap(), 142);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(TEST_INPUT1).unwrap(), 142);
+        assert_eq!(part2(TEST_INPUT2).unwrap(), 281);
+    }
+}

src/instrument.rs

@@ -0,0 +1,12 @@
+macro_rules! instrument {
+    ($part1:expr, $part2:expr) => {
+        let mut now = std::time::Instant::now();
+        println!("Part 1: {}", $part1);
+        println!("(elapsed: {:?})", now.elapsed());
+        now = std::time::Instant::now();
+        println!("");
+        println!("Part 2: {}", $part2);
+        println!("(elapsed: {:?})", now.elapsed());
+    };
+}
+pub(crate) use instrument;

src/main.rs

@@ -0,0 +1,10 @@
+pub mod day01;
+pub mod instrument;
+
+use anyhow::Result;
+
+fn main() -> Result<()> {
+    println!("Advent of Code 2023");
+    day01::solve()?;
+    Ok(())
+}