2017 day 8

Author: ictrobot

crates/year2017/src/day08.rs

@@ -0,0 +1,73 @@
+use std::collections::HashMap;
+use utils::prelude::*;
+
+/// Evaluating conditional add instructions.
+#[derive(Clone, Debug)]
+pub struct Day08 {
+    part1: i32,
+    part2: i32,
+}
+
+impl Day08 {
+    pub fn new(input: &str, _: InputType) -> Result<Self, InputError> {
+        let parsed = parser::take_while1(u8::is_ascii_lowercase)
+            .with_suffix(" ")
+            .then(
+                parser::one_of((
+                    parser::i32().with_prefix("inc "),
+                    parser::i32().with_prefix("dec ").map(|x| -x),
+                ))
+                .with_suffix(" if "),
+            )
+            .then(parser::take_while1(u8::is_ascii_lowercase).with_suffix(" "))
+            .then(
+                parser::one_of((
+                    "==".map(|_| i32::eq as fn(&i32, &i32) -> bool),
+                    "!=".map(|_| i32::ne as fn(&i32, &i32) -> bool),
+                    "<=".map(|_| i32::le as fn(&i32, &i32) -> bool),
+                    ">=".map(|_| i32::ge as fn(&i32, &i32) -> bool),
+                    "<".map(|_| i32::lt as fn(&i32, &i32) -> bool),
+                    ">".map(|_| i32::gt as fn(&i32, &i32) -> bool),
+                ))
+                .with_suffix(" "),
+            )
+            .then(parser::i32())
+            .parse_lines(input)?;
+
+        let mut registers = HashMap::new();
+        let mut max = 0;
+        for (reg, value, cond_reg, comparison, cond_value) in parsed {
+            if comparison(registers.entry(cond_reg).or_insert(0), &cond_value) {
+                let entry = registers.entry(reg).or_insert(0);
+                *entry += value;
+                max = max.max(*entry);
+            }
+        }
+
+        Ok(Self {
+            part1: registers.into_values().max().unwrap_or(0),
+            part2: max,
+        })
+    }
+
+    #[must_use]
+    pub fn part1(&self) -> i32 {
+        self.part1
+    }
+
+    #[must_use]
+    pub fn part2(&self) -> i32 {
+        self.part2
+    }
+}
+
+examples!(Day08 -> (i32, i32) [
+    {
+        input: "b inc 5 if a > 1\n\
+            a inc 1 if b < 5\n\
+            c dec -10 if a >= 1\n\
+            c inc -20 if c == 10",
+        part1: 1,
+        part2: 10
+    },
+]);

crates/year2017/src/lib.rs

@@ -9,4 +9,5 @@ utils::year!(2017 => year2017, ${
     5 => day05::Day05,
     6 => day06::Day06,
     7 => day07::Day07<'_>,
+    8 => day08::Day08,
 });