2023 day1/rust: add solution

2023/day1/rust/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "rust_2023_01"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+aoc = { path = "../../../common/rust" }

2023/day1/rust/src/main.rs

@@ -0,0 +1,65 @@
+#![warn(clippy::pedantic)]
+
+use std::io::stdin;
+
+const DIGIT_WORDS: [&str; 9] = [
+    "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
+];
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Direction {
+    Forward,
+    Backward,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum DigitMode {
+    NumeralsOnly,
+    NumeralsAndWords,
+}
+
+fn locate_digit(s: &str, direction: Direction, mode: DigitMode) -> usize {
+    let locate_digit = |n: usize, word| {
+        let locate = match direction {
+            Direction::Forward => str::find,
+            Direction::Backward => str::rfind,
+        };
+        let numeral = n.to_string();
+        let numeral_pos = locate(s, numeral.as_str());
+        let word_pos = if mode == DigitMode::NumeralsAndWords {
+            locate(s, word)
+        } else {
+            None
+        };
+        [numeral_pos, word_pos].into_iter().flatten()
+    };
+
+    let positions = DIGIT_WORDS.into_iter().enumerate().flat_map(|(n, word)| {
+        let n = n + 1;
+        locate_digit(n, word).map(move |pos| (pos, n))
+    });
+
+    match direction {
+        Direction::Forward => positions.min_by_key(|(pos, _)| *pos),
+        Direction::Backward => positions.max_by_key(|(pos, _)| *pos),
+    }
+    .unwrap()
+    .1
+}
+
+fn get_number(s: &str, mode: DigitMode) -> usize {
+    let first = locate_digit(s, Direction::Forward, mode);
+    let last = locate_digit(s, Direction::Backward, mode);
+    first * 10 + last
+}
+
+fn get_sum(lines: &[String], mode: DigitMode) -> usize {
+    lines.iter().map(|l| get_number(l, mode)).sum()
+}
+
+fn main() {
+    let lines: Vec<_> = stdin().lines().map(Result::unwrap).collect();
+
+    println!("{}", get_sum(&lines, DigitMode::NumeralsOnly));
+    println!("{}", get_sum(&lines, DigitMode::NumeralsAndWords));
+}

Cargo.lock

@@ -628,6 +628,13 @@ dependencies = [
  "strum",
 ]
 
+[[package]]
+name = "rust_2023_01"
+version = "0.1.0"
+dependencies = [
+ "aoc",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.11"

Cargo.toml

@@ -27,4 +27,5 @@ members = [
 	"2022/day14/rust",
 	"2022/day15/rust",
 	"2022/day18/rust",
+	"2023/day1/rust",
 ]