implement Day01

Day01/example_input.txt

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

Day01/src/main.rs

@@ -1,3 +1,60 @@
-fn main() {
-    println!("Hello, world!");
+use std::collections::HashMap;
+use std::fs::File;
+use std::io;
+use std::io::{BufRead, BufReader};
+
+fn main() -> io::Result<()> {
+    let file = File::open("input.txt")?;
+    let reader = BufReader::new(file);
+
+    let mut result = 0;
+
+    for line in reader.lines() {
+        let numbers = get_digits(line?);
+        result = result + (numbers.first().unwrap() * 10 + numbers.last().unwrap());
+    }
+
+    println!("First: {}", result);
+
+    let file = File::open("input.txt")?;
+    let reader = BufReader::new(file);
+    let mut result = 0;
+    for line in reader.lines() {
+        let replaced_line = replace_numbers(line?);
+        let numbers = get_digits(replaced_line);
+        result = result + (numbers.first().unwrap() * 10 + numbers.last().unwrap());
+    }
+    println!("Second: {}", result);
+
+    Ok(())
 }
+
+fn replace_numbers(input: String) -> String {
+    let map = HashMap::from([
+        ("one", "1"), ("two", "2"), ("three", "3"), ("four", "4"), ("five", "5"), ("six", "6"), ("seven", "7"), ("eight", "8"), ("nine", "9")
+    ]);
+    let mut result = input.clone();
+    for (from, to) in map {
+        let mut replacement = from.to_owned();
+        replacement.push_str(to);
+        replacement.push_str(from);
+        result = result.replace(from, &replacement);
+    }
+    result
+}
+
+fn get_digits(line: String) -> Vec<u32> {
+    line.chars().filter_map(|a| a.to_digit(10)).collect()
+}
+
+
+#[cfg(test)]
+mod tests {
+    use crate::replace_numbers;
+
+    #[test]
+    fn check_replace_numbers() {
+        let result = replace_numbers("twone".to_string());
+        assert_eq!(result, "two2twone1one");
+    }
+}