Implement 2023 day 2 part 1

2023/src/common.rs

@@ -16,6 +16,14 @@ use nom::IResult;
 use nom::InputLength;
 use nom::Parser;
 
+pub fn convert_nom_error(e: nom::error::Error<&[u8]>) -> anyhow::Error {
+    anyhow::anyhow!(
+        "Parser error {:?} to parse at {}",
+        e.code,
+        String::from_utf8_lossy(e.input)
+    )
+}
+
 /// 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
@@ -24,13 +32,7 @@ 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| {
+    let (unparsed, output) = parser.parse(input).finish().map_err(convert_nom_error)?;
-        anyhow::anyhow!(
-            "Parser error {:?} to parse at {}",
-            e.code,
-            String::from_utf8_lossy(e.input)
-        )
-    })?;
 
     if !unparsed.is_empty() {
         Err(anyhow::anyhow!(

2023/src/day02.rs

@@ -1,5 +1,78 @@
-pub fn part1(_input: &[u8]) -> anyhow::Result<String> {
+use nom::branch::alt;
-    anyhow::bail!("Not implemented")
+use nom::bytes::complete::tag;
+use nom::character::complete::newline;
+use nom::combinator::iterator;
+use nom::combinator::opt;
+use nom::combinator::value;
+use nom::multi::fold_many1;
+use nom::multi::many1;
+use nom::sequence::preceded;
+use nom::sequence::separated_pair;
+use nom::sequence::terminated;
+use nom::IResult;
+
+use crate::common::convert_nom_error;
+use crate::common::parse_input;
+
+#[derive(Clone, Copy)]
+#[repr(usize)]
+enum Color {
+    Red,
+    Green,
+    Blue,
+}
+
+fn parse_game(i: &[u8]) -> IResult<&[u8], (u8, [u8; 3])> {
+    let parse_color = terminated(
+        separated_pair(
+            nom::character::complete::u8,
+            tag(" "),
+            alt((
+                value(Color::Red, tag("red")),
+                value(Color::Green, tag("green")),
+                value(Color::Blue, tag("blue")),
+            )),
+        ),
+        opt(alt((tag(", "), tag("; ")))),
+    );
+
+    separated_pair(
+        preceded(tag("Game "), nom::character::complete::u8),
+        tag(": "),
+        terminated(
+            fold_many1(
+                parse_color,
+                || [0u8; 3],
+                |mut cur, (value, color)| {
+                    cur[color as usize] = Ord::max(cur[color as usize], value);
+                    cur
+                },
+            ),
+            newline,
+        ),
+    )(i)
+}
+
+pub fn part1(input: &[u8]) -> anyhow::Result<String> {
+    let mut game_it = iterator(input, parse_game);
+
+    let total: u32 = game_it
+        .into_iter()
+        .filter_map(|(id, colors)| {
+            if colors[0] <= 12 && colors[1] <= 13 && colors[2] <= 14 {
+                Some(u32::from(id))
+            } else {
+                None
+            }
+        })
+        .sum();
+
+    game_it.finish().map_err(|e| match e {
+        nom::Err::Incomplete(_) => anyhow::anyhow!("unreachable"),
+        nom::Err::Failure(e) | nom::Err::Error(e) => convert_nom_error(e),
+    })?;
+
+    Ok(total.to_string())
 }
 
 pub fn part2(_input: &[u8]) -> anyhow::Result<String> {

2023/src/samples/02.txt

@@ -0,0 +1,5 @@
+Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green
+Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue
+Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
+Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
+Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green