Prepare AOC

src/lib.rs

@@ -0,0 +1,108 @@
+//! This library contains useful helper functions that may be useful in several problems.
+
+use std::{
+    fmt::{Debug, Display},
+    ops::{Div, Mul, Rem},
+    str::FromStr,
+};
+
+/// Parse a whitespace separated list of things.
+///
+/// This works with any type that implements [`FromStr`].
+///
+/// Panics on parse error to keep things simple.
+///
+/// ```rust
+/// # use aoc::parse_ws_separated;
+/// let mut nums = parse_ws_separated("1 2 3");
+/// assert_eq!(nums.next(), Some(1));
+/// assert_eq!(nums.next(), Some(2));
+/// assert_eq!(nums.next(), Some(3));
+/// assert_eq!(nums.next(), None);
+/// ```
+///
+/// ```rust
+/// # use aoc::parse_ws_separated;
+/// # use std::net::Ipv4Addr;
+/// let mut ips = parse_ws_separated("127.0.0.1      10.0.0.1");
+/// assert_eq!(ips.next(), Some(Ipv4Addr::new(127, 0, 0, 1)));
+/// assert_eq!(ips.next(), Some(Ipv4Addr::new(10, 0, 0, 1)));
+/// assert_eq!(ips.next(), None);
+/// ```
+pub fn parse_ws_separated<T>(s: &str) -> impl DoubleEndedIterator<Item = T> + '_
+where
+    T: FromStr,
+    <T as FromStr>::Err: Debug,
+{
+    s.split_ascii_whitespace().map(|s| s.parse().unwrap())
+}
+
+/// Concatenate two things.
+///
+/// Panics if the concatenation is not be parseable to keep things simple.
+///
+/// ```rust
+/// # use aoc::concat;
+/// assert_eq!(concat(123, 456), 123456);
+/// ```
+pub fn concat<T>(a: T, b: T) -> T
+where
+    T: Display + FromStr,
+    <T as FromStr>::Err: Debug,
+{
+    format!("{a}{b}").parse().unwrap()
+}
+
+/// Return the greatest common divisor.
+///
+/// <https://en.wikipedia.org/wiki/Euclidean_algorithm>
+///
+/// ```rust
+/// # use aoc::gcd;
+/// assert_eq!(gcd(12, 8), 4);
+/// # assert_eq!(gcd(105, 252), 21);
+/// # assert_eq!(gcd(252, 105), 21);
+/// ```
+pub fn gcd<T>(mut a: T, mut b: T) -> T
+where
+    T: PartialEq + Default + Rem<Output = T> + Copy,
+{
+    let zero = T::default();
+    while b != zero {
+        (a, b) = (b, a % b);
+    }
+
+    a
+}
+
+/// Return the least common multiple.
+///
+/// <https://en.wikipedia.org/wiki/Least_common_multiple>
+///
+/// ```rust
+/// # use aoc::lcm;
+/// assert_eq!(lcm(4, 6), 12);
+/// # assert_eq!(lcm(6, 4), 12);
+/// ```
+pub fn lcm<T>(a: T, b: T) -> T
+where
+    T: PartialEq + Default + Rem<Output = T> + Div<Output = T> + Mul<Output = T> + Copy,
+{
+    let gcd = gcd(a, b);
+    a / gcd * b
+}
+
+/// Given a function and a name of a file in the `input` directory,
+/// assert that the function applied to the contents of the file returns the expected result.
+#[macro_export]
+macro_rules! assert_example {
+    ($solve:ident, $file:expr, $expected:expr) => {
+        assert_eq!(
+            $solve(include_str!(concat!("../../input/", $file))),
+            $expected,
+            "{}, {}",
+            stringify!($solve),
+            $file,
+        )
+    };
+}