2017 day 2

Author: ictrobot

crates/utils/src/input.rs

@@ -48,6 +48,7 @@ impl InputError {
     pub fn new(input: &str, index: impl ToIndex, source: impl Into<Box<dyn Error>>) -> Self {
         let index = index.input_index(input);
         let (line_number, column_number, line) = Self::line_position(input, index);
+        let line = line.replace('\t', " ");
 
         InputError {
             line_number,

crates/utils/src/parser/base.rs

@@ -1,5 +1,7 @@
 use crate::input::{InputError, MapWithInputExt};
-use crate::parser::combinator::{Map, MapResult, Optional, Or, Repeat, WithPrefix, WithSuffix};
+use crate::parser::combinator::{
+    Map, MapResult, Optional, Or, RepeatN, RepeatVec, WithPrefix, WithSuffix,
+};
 use crate::parser::error::WithErrorMsg;
 use crate::parser::simple::Eol;
 use crate::parser::then::Then2;
@@ -152,24 +154,72 @@ pub trait Parser: Sized {
         Optional { parser: self }
     }
 
-    /// Repeat this parser `N` times, returning an array.
+    /// Repeat this parser `N` times, returning an [`array`].
+    ///
+    /// See also [`repeat`](Self::repeat) which returns a [`Vec`] instead, for unknown or varying
+    /// number of repeats.
     ///
     /// # Examples
     /// ```
     /// # use utils::parser::{self, Parser};
     /// assert_eq!(
     ///     parser::u32()
     ///         .with_suffix(",".optional())
-    ///         .repeat() // N = 3 is inferred
+    ///         .repeat_n() // N = 3 is inferred
     ///         .parse(b"12,34,56"),
     ///     Ok(([12, 34, 56], &b""[..]))
     /// );
     /// ```
-    fn repeat<const N: usize>(self) -> Repeat<N, Self>
+    fn repeat_n<const N: usize>(self) -> RepeatN<N, Self>
     where
         for<'i> Self::Output<'i>: Copy + Default,
     {
-        Repeat { parser: self }
+        RepeatN { parser: self }
+    }
+
+    /// Repeat this parser while it matches, returning a [`Vec`].
+    ///
+    /// If the number of items is constant and known in advance, prefer [`repeat_n`](Self::repeat_n)
+    /// as it avoids allocating.
+    ///
+    /// See also [`repeat_min`](Self::repeat_min), which ensures at least N items are parsed.
+    ///
+    /// # Examples
+    /// ```
+    /// # use utils::parser::{self, Parser};
+    /// assert_eq!(
+    ///     parser::u32()
+    ///         .with_suffix(",".optional())
+    ///         .repeat()
+    ///         .parse(b"12,34,56,78"),
+    ///     Ok((vec![12, 34, 56, 78], &b""[..]))
+    /// );
+    /// ```
+    fn repeat(self) -> RepeatVec<Self> {
+        RepeatVec {
+            parser: self,
+            min_elements: 0,
+        }
+    }
+
+    /// Repeat this parser at least N times, returning a [`Vec`].
+    ///
+    /// See also [`repeat`](Self::repeat).
+    ///
+    /// # Examples
+    /// ```
+    /// # use utils::parser::{self, Parser};
+    /// let parser = parser::u32()
+    ///     .with_suffix(",".optional())
+    ///     .repeat_min(3);
+    /// assert_eq!(parser.parse(b"12,34,56,78"), Ok((vec![12, 34, 56, 78], &b""[..])));
+    /// assert!(parser.parse(b"12,34").is_err());
+    /// ```
+    fn repeat_min(self, min_elements: usize) -> RepeatVec<Self> {
+        RepeatVec {
+            parser: self,
+            min_elements,
+        }
     }
 
     /// Parse a prefix (normally a string literal) before this parser.

crates/utils/src/parser/combinator.rs

@@ -74,10 +74,10 @@ impl<P: Parser> Parser for Optional<P> {
 }
 
 #[derive(Copy, Clone)]
-pub struct Repeat<const N: usize, P> {
+pub struct RepeatN<const N: usize, P> {
     pub(super) parser: P,
 }
-impl<const N: usize, P: for<'i> Parser<Output<'i>: Copy + Default>> Parser for Repeat<N, P> {
+impl<const N: usize, P: for<'i> Parser<Output<'i>: Copy + Default>> Parser for RepeatN<N, P> {
     type Output<'i> = [P::Output<'i>; N];
     type Then<T: Parser> = Then2<Self, T>;
 
@@ -101,6 +101,34 @@ impl<const N: usize, P: for<'i> Parser<Output<'i>: Copy + Default>> Parser for R
     }
 }
 
+#[derive(Copy, Clone)]
+pub struct RepeatVec<P> {
+    pub(super) parser: P,
+    pub(super) min_elements: usize,
+}
+impl<P: Parser> Parser for RepeatVec<P> {
+    type Output<'i> = Vec<P::Output<'i>>;
+    type Then<T: Parser> = Then2<Self, T>;
+
+    #[inline]
+    fn parse<'i>(&self, mut input: &'i [u8]) -> ParseResult<'i, Self::Output<'i>> {
+        let mut output = Vec::new();
+        while let Ok((v, remaining)) = self.parser.parse(input) {
+            output.push(v);
+            input = remaining;
+        }
+        if output.len() >= self.min_elements {
+            Ok((output, input))
+        } else {
+            Err((ParseError::ExpectedMatches(self.min_elements), input))
+        }
+    }
+
+    fn then<T: Parser>(self, next: T) -> Self::Then<T> {
+        Then2::new(self, next)
+    }
+}
+
 #[derive(Copy, Clone)]
 pub struct Or<A, B> {
     pub(super) first: A,

crates/year2016/src/day03.rs

@@ -11,7 +11,7 @@ impl Day03 {
         Ok(Self {
             input: parser::u32()
                 .with_prefix(parser::take_while(u8::is_ascii_whitespace))
-                .repeat()
+                .repeat_n()
                 .parse_lines(input)?,
         })
     }

crates/year2016/src/day22.rs

@@ -35,7 +35,7 @@ impl Day22 {
                 parser::u32()
                     .with_prefix(parser::take_while1(u8::is_ascii_whitespace))
                     .with_suffix(b'T')
-                    .repeat::<3>(),
+                    .repeat_n::<3>(),
             )
             .map_res(|(x, y, [size, used, avail])| {
                 if size == used + avail {

crates/year2017/src/day02.rs

@@ -0,0 +1,52 @@
+use utils::prelude::*;
+
+/// Calculating spreadsheet checksums.
+#[derive(Clone, Debug)]
+pub struct Day02 {
+    rows: Vec<Vec<u32>>,
+}
+
+impl Day02 {
+    pub fn new(input: &str, _: InputType) -> Result<Self, InputError> {
+        Ok(Self {
+            rows: parser::u32()
+                .with_suffix(b' '.or(b'\t').optional())
+                .repeat_min(2)
+                .map(|mut v| {
+                    v.sort_unstable();
+                    v
+                })
+                .parse_lines(input)?,
+        })
+    }
+
+    #[must_use]
+    pub fn part1(&self) -> u32 {
+        self.rows
+            .iter()
+            .map(|row| row[row.len() - 1] - row[0])
+            .sum()
+    }
+
+    #[must_use]
+    pub fn part2(&self) -> u32 {
+        self.rows
+            .iter()
+            .map(|row| {
+                for i in 0..row.len() - 1 {
+                    for j in i + 1..row.len() {
+                        if row[j] % row[i] == 0 {
+                            return row[j] / row[i];
+                        }
+                    }
+                }
+                panic!("no solution found")
+            })
+            .sum()
+    }
+}
+
+examples!(Day02 -> (u32, u32) [
+    {input: "5 1 9 5\n7 5 3\n2 4 6 8", part1: 18},
+    {input: "5 9 2 8\n9 4 7 3\n3 8 6 5", part2: 9},
+]);

crates/year2017/src/lib.rs

@@ -3,4 +3,5 @@
 
 utils::year!(2017 => year2017, ${
     1 => day01::Day01<'_>,
+    2 => day02::Day02,
 });