feat: solve day 2 part 1

src/day2.rs

@@ -0,0 +1,74 @@
+use std::fs::File;
+use std::io::{prelude::*, self};
+use std::num::ParseIntError;
+
+#[derive(Debug)]
+pub enum InputFromFileError {
+    ParseCommandError,
+    ParseIntError(ParseIntError),
+    IoError(io::Error),
+}
+
+pub enum Command {
+    Forward,
+    Down,
+    Up
+}
+
+pub struct CommandLine(Command, u32);
+
+fn parse_line(line: &str) -> Result<CommandLine, InputFromFileError> {
+    let parts: Vec<&str> = line.split(' ').collect();
+    let command = match parts[0] {
+        "up" => Ok(Command::Up),
+        "down" => Ok(Command::Down),
+        "forward" => Ok(Command::Forward),
+        _ => Err(InputFromFileError::ParseCommandError)
+    }?;
+    let amount = parts[1].parse().map_err(InputFromFileError::ParseIntError)?;
+    Ok(CommandLine(command, amount))
+}
+
+pub fn input_from_file(filename: &str) -> Result<Vec<CommandLine>, InputFromFileError> {
+    let mut file = File::open(filename).map_err(InputFromFileError::IoError)?;
+
+    let mut contents = String::new();
+    file.read_to_string(&mut contents).map_err(InputFromFileError::IoError)?;
+
+    contents.split_terminator('\n')
+        .map(parse_line)
+        .collect()
+}
+
+pub fn part1(commands: &[CommandLine]) -> u32 {
+    let mut depth = 0;
+    let mut horizontal = 0;
+    for command in commands {
+        match command.0 {
+            Command::Up      => depth -= command.1,
+            Command::Down    => depth += command.1,
+            Command::Forward => horizontal += command.1,
+        }
+    }
+    return depth * horizontal;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        let commands = [
+            CommandLine(Command::Forward, 5),
+            CommandLine(Command::Down, 5),
+            CommandLine(Command::Forward, 8),
+            CommandLine(Command::Up, 3),
+            CommandLine(Command::Down, 8),
+            CommandLine(Command::Forward, 2)
+        ];
+        let result = part1(&commands);
+        assert_eq!(result, 150);
+    }
+}
+

src/main.rs

@@ -1,12 +1,18 @@
 mod day1;
+mod day2;
 
 fn main() {
-    let input_filename = "input.txt";
-    let input = day1::input_from_file(input_filename)
-        .expect("Failed to read input.txt");
-    let result1 = day1::part1(&input);
-    let result2 = day1::part2(&input);
+    let input_filename = "input2.txt";
+    let input = day2::input_from_file(input_filename)
+        .expect("Failed to read input2.txt");
+
+    // let result1 = day1::part1(&input);
+    // let result2 = day1::part2(&input);
+    
+    let result1 = day2::part1(&input);
+    // let result2 = day2::part2(&input);
+
     println!("Part 1 result: {}", result1);
-    println!("Part 2 result: {}", result2);
+    // println!("Part 2 result: {}", result2);
 }