Rewrite old code into 2018 style.

Nice test for my 2018 repo set up. Which turns out needs some tweaking.

2016/src/common.rs

@@ -0,0 +1,63 @@
+use std::io;
+
+/// Apply Erathostenes's sieve to the supplied array
+///
+/// # Arguments
+///
+/// * `dest` - the destination slice to fill with the sieve. This is
+///   assumed to be filled with "true" before being handed to this
+///   method.
+pub fn prime_sieve(dest: &mut[bool]) {
+    if dest.len() >= 1 {
+        dest[0] = false;
+    }
+
+    if dest.len() >= 2 {
+        dest[1] = false;
+    }
+
+    let limit = (dest.len() as f64).sqrt() as usize;
+
+    for i in 1..(limit + 1) {
+        if !dest[i] {
+            continue
+        }
+
+        for j in ((i * i)..(dest.len())).step_by(i) {
+            dest[j] = false;
+        }
+    }
+}
+
+/// Solution trait
+///
+/// Every day's solution should implement this function so that it can
+/// be easily run from the main program.
+pub trait Solution {
+    /// Solve the first part of the day
+    fn part1(&mut self, input: &mut io::Read) -> String;
+
+    /// Solve the second part of the day
+    fn part2(&mut self, input: &mut io::Read) -> String;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_prime_sieve() {
+        let mut input = [true; 10];
+        prime_sieve(&mut input);
+
+        let output = [
+            false, false,
+            true, true,
+            false, true,
+            false, true,
+            false, false
+        ];
+
+        assert_eq!(output, input);
+    }
+}

2016/src/day1.rs

@@ -0,0 +1,112 @@
+use std::io;
+use common;
+use std::collections::HashSet;
+use std::error::Error;
+
+
+fn dist(pos: (i32, i32)) -> i32 {
+    let (x, y) = pos;
+
+    return x.abs() + y.abs()
+}
+
+pub struct Day1 {
+    pos: (i32, i32),
+    dir: i32,
+}
+
+impl Day1 {
+    pub fn new() -> Day1 {
+        Day1{
+            pos: (0, 0),
+            dir: (0),
+        }
+    }
+
+    fn walk(&mut self) -> (i32, i32) {
+        let backwards = if self.dir & 2 == 2 { -1 } else { 1 };
+        let (x, y) = self.pos;
+
+        self.pos = (x + backwards * (1 - (self.dir & 1)), y + backwards * (self.dir & 1));
+        self.pos
+    }
+
+    fn turn(&mut self, action: &str) {
+        if action == "R" {
+            self.dir += 1;
+        } else {
+            self.dir += 3;
+        }
+        self.dir %= 4;
+    }
+}
+
+impl common::Solution for Day1 {
+    fn part1(&mut self, input: &mut io::Read) -> String {
+        let mut content = String::new();
+        match input.read_to_string(&mut content) {
+            Err(why) => panic!("couldn't open input: {}", why.description()),
+            Ok(_) => {},
+        };
+
+        for instruction in content.split(", ") {
+            let turn = &instruction[..1];
+            let steps: i32 = instruction[1..].trim().parse().expect("Invalid number of steps");
+            self.turn(turn);
+
+            for _ in 0..steps {
+                self.walk();
+            }
+        }
+
+        format!("{}", dist(self.pos))
+    }
+
+    fn part2(&mut self, input: &mut io::Read) -> String {
+        let mut content = String::new();
+        match input.read_to_string(&mut content) {
+            Err(why) => panic!("couldn't open input: {}", why.description()),
+            Ok(_) => {},
+        };
+
+        let mut positions = HashSet::new();
+        positions.insert(self.pos);
+
+        for instruction in content.split(", ") {
+            let turn = &instruction[..1];
+            let steps: i32 = instruction[1..].trim().parse().expect("Invalid number of steps");
+            self.turn(turn);
+
+            for _ in 0..steps {
+                let pos = self.walk();
+                if positions.contains(&pos) {
+                    return format!("{}", dist(pos))
+                } else {
+                    positions.insert(pos);
+                }
+            }
+        }
+
+        panic!("Never visited anything twice!")
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Day1;
+    use common::Solution;
+
+    #[test]
+    fn sample_part1() {
+        let mut instance = Day1::new();
+
+        assert_eq!("8", instance.part1(&mut "R8, R4, R4, R8".as_bytes()))
+    }
+
+    #[test]
+    fn sample_part2() {
+        let mut instance = Day1::new();
+
+        assert_eq!("4", instance.part2(&mut "R8, R4, R4, R8".as_bytes()))
+    }
+}

2016/src/main.rs

@@ -0,0 +1,65 @@
+extern crate clap;
+use clap::{Arg, App};
+use std::fs;
+use std::io;
+
+pub mod common;
+pub mod day1;
+
+fn get_impl(day: i32) -> Box<common::Solution> {
+    match day {
+        1 => { Box::new(day1::Day1::new()) }
+        _ => {
+            panic!("Unimplemented day {}", day)
+        }
+    }
+}
+
+fn main() {
+    let matches = App::new("Advent of Code")
+        .version("2016")
+        .author("Bert Peters <bert@bertptrs.nl>")
+        .arg(Arg::with_name("day")
+             .value_name("DAY")
+             .help("Number of the day to execute")
+             .required(true)
+             .takes_value(true))
+        .arg(Arg::with_name("part2")
+             .short("2")
+             .help("Whether to run part 2")
+             .long("part2"))
+        .arg(Arg::with_name("input")
+             .short("i")
+             .long("input")
+             .help("Optional input file, stdin otherwise")
+             .takes_value(true))
+        .get_matches();
+
+    let day: i32 = (&matches.value_of("day").unwrap()).parse()
+        .expect("Invalid int");
+    let mut implementation = get_impl(day);
+    let mut data: Box<io::Read> = match matches.value_of("input") {
+        Some(filename) => { Box::new(fs::File::open(filename).unwrap()) }
+        None => { Box::new(io::stdin()) }
+    };
+
+    if matches.is_present("part2") {
+        println!("{}", implementation.part2(&mut data));
+    } else {
+        println!("{}", implementation.part1(&mut data));
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_impl() {
+        // Verify that we can load all days
+        let last_implemented = 1;
+        for d in 1..(last_implemented + 1) {
+            get_impl(d);
+        }
+    }
+}