init

day1/Cargo.toml

@@ -0,0 +1,9 @@
+[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]
+regex = "1.10.2"

day1/src/main.rs

@@ -0,0 +1,52 @@
+use std::fs::read_to_string;
+use std::collections::HashMap;
+use regex::Regex;
+
+fn get_digit(text: &str, digits_map: &HashMap<&str, i32>) -> i32 {
+    match text.parse::<i32>() {
+        Ok(num) => {
+            num
+        }
+        Err(_) => {
+            digits_map[text]
+        }
+    }
+}
+
+fn main() {
+    let digits_map: HashMap<&str, i32> = HashMap::from([
+        ("one", 1), ("two", 2), ("three", 3), ("four", 4), ("five", 5),
+        ("six", 6), ("seven", 7), ("eight", 8), ("nine", 9)
+    ]);
+    let mut sum1 = 0;
+    let mut sum2 = 0;
+    let forward_re = Regex::new("[0-9]|one|two|three|four|five|six|seven|eight|nine").unwrap();
+    let backward_re = Regex::new(&("[0-9]|".to_owned()
+        + &"one|two|three|four|five|six|seven|eight|nine".chars().rev().collect::<String>())).unwrap();
+    for line in read_to_string("input.txt").unwrap().lines() {
+        // First task
+        let mut first_digit: i32 = -1;
+        let mut last_digit: i32 = -1;
+        for c in line.chars() {
+            match c.to_digit(10) {
+                Some(num) => {
+                    if first_digit < 0 {
+                        first_digit = num as i32;
+                    }
+                    last_digit = num as i32;
+                },
+                None => {}
+            }
+        }
+        sum1 += first_digit * 10 + last_digit;
+
+        // Second task
+        let first_digit2 = get_digit(forward_re.find(line).unwrap().as_str(), &digits_map);
+        let last_digit2 = get_digit(
+            &backward_re.find(&line.chars().rev().collect::<String>())
+                .unwrap().as_str().chars().rev().collect::<String>(), &digits_map);
+        sum2 += first_digit2 * 10 + last_digit2;
+    }
+    println!("Sum 1: {}", sum1);
+    println!("Sum 2: {}", sum2);
+}