Add skeletons for all days

2023/src/common.rs

@@ -0,0 +1,234 @@
+//! Common helper utilities to all days
+
+use std::cmp::Ordering;
+use std::ops::Add;
+use std::ops::Div;
+use std::ops::Index;
+use std::ops::IndexMut;
+use std::ops::Sub;
+
+use anyhow::Result;
+use nom::combinator::map;
+use nom::error::ErrorKind;
+use nom::error::ParseError;
+use nom::Finish;
+use nom::IResult;
+use nom::InputLength;
+use nom::Parser;
+
+/// Parse input from some nom parser and return as an anyhow result
+///
+/// This method exists as a convenience because nom's errors cannot otherwise be easily converted to
+/// an anyhow error, and I don't want to keep track of custom error implementations here.
+pub fn parse_input<'a, O>(
+    input: &'a [u8],
+    mut parser: impl Parser<&'a [u8], O, nom::error::Error<&'a [u8]>>,
+) -> Result<O> {
+    let (unparsed, output) = parser.parse(input).finish().map_err(|e| {
+        anyhow::anyhow!(
+            "Parser error {:?} to parse at {}",
+            e.code,
+            String::from_utf8_lossy(e.input)
+        )
+    })?;
+
+    if !unparsed.is_empty() {
+        Err(anyhow::anyhow!(
+            "Not all input consumed: {}",
+            String::from_utf8_lossy(unparsed)
+        ))
+    } else {
+        Ok(output)
+    }
+}
+
+/// Applies a parser iteratively and reduces the results using the given function. Fails if the
+/// embedded parser doesn't return at least one result.
+///
+/// # Arguments
+/// - `f`: the function to apply
+/// - `g`: the function that combines the result o `f` with previous results
+///
+/// This implementation is based on [`nom::multi::fold_many1`] with minor differences. If
+/// successful, this should probably be upstreamed.
+pub fn reduce_many1<I, O, E, F>(
+    mut f: F,
+    mut g: impl FnMut(O, O) -> O,
+) -> impl FnMut(I) -> IResult<I, O, E>
+where
+    I: Clone + InputLength,
+    E: ParseError<I>,
+    F: Parser<I, O, E>,
+{
+    // Cannot delegate to fold_many0 because that would make the function FnOnce rather than FnMut,
+    // since it would transfer ownership of the embedded parser to fold_many0.
+    move |i: I| {
+        let _i = i.clone();
+        match f.parse(_i) {
+            Err(nom::Err::Error(_)) => {
+                Err(nom::Err::Error(E::from_error_kind(i, ErrorKind::Many1)))
+            }
+            Err(e) => Err(e),
+            Ok((i1, mut acc)) => {
+                let mut input = i1;
+
+                loop {
+                    let _input = input.clone();
+                    let len = input.input_len();
+                    match f.parse(_input) {
+                        Err(nom::Err::Error(_)) => {
+                            break;
+                        }
+                        Err(e) => return Err(e),
+                        Ok((i, o)) => {
+                            // infinite loop check: the parser must always consume
+                            if i.input_len() == len {
+                                return Err(nom::Err::Failure(E::from_error_kind(
+                                    i,
+                                    ErrorKind::Many1,
+                                )));
+                            }
+
+                            acc = g(acc, o);
+                            input = i;
+                        }
+                    }
+                }
+
+                Ok((input, acc))
+            }
+        }
+    }
+}
+
+/// Add an index to repeated successful invocations of the embedded parser.
+pub fn enumerate<I, O, E>(f: impl Parser<I, O, E>) -> impl FnMut(I) -> IResult<I, (usize, O), E> {
+    let mut index = 0usize;
+
+    map(f, move |v| {
+        let res = (index, v);
+        index += 1;
+        res
+    })
+}
+
+/// Return the minimum and maximum of two unordered variables
+pub fn minmax<T>(a: T, b: T) -> (T, T)
+where
+    T: PartialOrd,
+{
+    if a < b {
+        (a, b)
+    } else {
+        (b, a)
+    }
+}
+
+/// Some magic to get two mutable references into the same slice
+pub fn get_both<T>(slice: &mut [T], first: usize, second: usize) -> (&mut T, &mut T) {
+    match first.cmp(&second) {
+        Ordering::Greater => {
+            let (begin, end) = slice.split_at_mut(first);
+            (&mut end[0], &mut begin[second])
+        }
+        Ordering::Less => {
+            let (begin, end) = slice.split_at_mut(second);
+            (&mut begin[first], &mut end[0])
+        }
+        Ordering::Equal => panic!("Tried to get the same index twice {first}"),
+    }
+}
+
+#[derive(Debug, Default)]
+pub struct IndexSet(Vec<u32>);
+
+impl IndexSet {
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self(Vec::with_capacity(
+            capacity / std::mem::size_of::<u32>() / 8,
+        ))
+    }
+
+    fn ensure_item(&mut self, item: usize) -> &mut u32 {
+        if self.0.len() <= item {
+            self.0.resize(item + 1, 0);
+        }
+
+        &mut self.0[item]
+    }
+
+    #[inline]
+    fn index(index: usize) -> (usize, u8) {
+        const PER_ENTRY: usize = 8 * std::mem::size_of::<u32>();
+
+        (index / PER_ENTRY, (index % PER_ENTRY) as u8)
+    }
+
+    pub fn insert(&mut self, index: usize) -> bool {
+        let (entry, pos) = Self::index(index);
+
+        let item = self.ensure_item(entry);
+        let old = *item;
+
+        *item |= 1 << pos;
+
+        old != *item
+    }
+
+    pub fn contains(&self, index: usize) -> bool {
+        let (entry, pos) = Self::index(index);
+
+        self.0
+            .get(entry)
+            .map_or(false, |&entry| (entry & (1 << pos) != 0))
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Vec2(pub [i32; 2]);
+
+impl Vec2 {
+    pub fn l1(self) -> i32 {
+        self.0.into_iter().map(i32::abs).sum()
+    }
+}
+
+impl Add<Self> for Vec2 {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        Self([self[0] + rhs[0], self[1] + rhs[1]])
+    }
+}
+
+impl Sub<Self> for Vec2 {
+    type Output = Self;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        Self([self[0] - rhs[0], self[1] - rhs[1]])
+    }
+}
+
+impl Div<i32> for Vec2 {
+    type Output = Self;
+
+    fn div(self, rhs: i32) -> Self::Output {
+        Self(self.0.map(|v| v / rhs))
+    }
+}
+
+impl Index<usize> for Vec2 {
+    type Output = i32;
+
+    #[inline]
+    fn index(&self, index: usize) -> &Self::Output {
+        &self.0[index]
+    }
+}
+
+impl IndexMut<usize> for Vec2 {
+    #[inline]
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        &mut self.0[index]
+    }
+}