day2 puzzle 1

day2/.gitignore

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+/target

day2/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day2"
+version = "0.1.0"

day2/Cargo.toml

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+[package]
+name = "day2"
+version = "0.1.0"
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day2/src/main.rs

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+mod models;
+
+use models::{Command, Submarine};
+use std::fs::File;
+use std::io::{self, BufRead, BufReader, Lines, Result};
+use std::iter::Iterator;
+use std::path::Path;
+
+static INPUT_PATH: &str = "input.txt";
+
+fn main() -> Result<()> {
+    let submarine = Submarine { xcord: 0, depth: 0 };
+    let commands = read_commands(INPUT_PATH)?;
+    let submarine = apply_commands(submarine, &commands);
+    println!("First puzzle: {}", submarine.depth * submarine.xcord);
+    Ok(())
+}
+
+fn apply_commands(submarine: Submarine, commands: &[Command]) -> Submarine {
+    commands.iter().copied().fold(submarine, Submarine::exec)
+}
+
+fn read_commands(file_path: &str) -> Result<Vec<Command>> {
+    read_lines(file_path).map(lines_to_commands)
+}
+
+fn lines_to_commands(lines: Lines<BufReader<File>>) -> Vec<Command> {
+    lines
+        .filter_map(|line| line.ok().map(Command::from))
+        .collect()
+}
+
+// The output is wrapped in a Result to allow matching on errors
+// Returns an Iterator to the Reader of the lines of the file.
+fn read_lines<P>(filename: P) -> io::Result<Lines<BufReader<File>>>
+where
+    P: AsRef<Path>,
+{
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}

day2/src/models/mod.rs

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+#[derive(Debug, Clone, Copy)]
+pub struct Submarine {
+    pub xcord: i32,
+    pub depth: i32,
+}
+
+impl Submarine {
+    pub fn exec(submarine: Self, command: Command) -> Self {
+        match command {
+            Command::Forward(unit) => Self::forward(submarine, unit),
+            Command::Down(unit) => Self::down(submarine, unit),
+            Command::Up(unit) => Self::up(submarine, unit),
+        }
+    }
+
+    fn forward(submarine: Self, unit: i32) -> Self {
+        Submarine {
+            xcord: submarine.xcord + unit,
+            depth: submarine.depth,
+        }
+    }
+
+    fn down(submarine: Self, unit: i32) -> Self {
+        Submarine {
+            xcord: submarine.xcord,
+            depth: submarine.depth + unit,
+        }
+    }
+
+    fn up(submarine: Self, unit: i32) -> Self {
+        Submarine {
+            xcord: submarine.xcord,
+            depth: submarine.depth - unit,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum Command {
+    Forward(i32),
+    Down(i32),
+    Up(i32),
+}
+
+impl From<String> for Command {
+    fn from(str: String) -> Self {
+        let words: Vec<&str> = str.split_ascii_whitespace().collect();
+        let action = words[0];
+        let unit: i32 = words[1].parse().unwrap();
+        match action {
+            "forward" => Command::Forward(unit),
+            "down" => Command::Down(unit),
+            "up" => Command::Up(unit),
+            _ => panic!("Invalid command {}", action),
+        }
+    }
+}