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author | June McEnroe <june@causal.agency> | 2016-12-12 00:33:31 -0500 |
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committer | June McEnroe <june@causal.agency> | 2020-11-22 00:14:25 -0500 |
commit | 21721291d94d3c43247544b7024429d0a7288dac (patch) | |
tree | 7864318b733b8fc2321c950fdb8bd3bea46d5927 /src/bin/day12.rs | |
parent | Day 10 part 2 (diff) | |
download | aoc-21721291d94d3c43247544b7024429d0a7288dac.tar.gz aoc-21721291d94d3c43247544b7024429d0a7288dac.zip |
Day 12
Diffstat (limited to '')
-rw-r--r-- | src/bin/day12.rs | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/src/bin/day12.rs b/src/bin/day12.rs new file mode 100644 index 0000000..64b09f8 --- /dev/null +++ b/src/bin/day12.rs @@ -0,0 +1,135 @@ +use std::io::{self, Read}; +use std::str::FromStr; + +#[derive(Clone, Copy)] +enum Operand { + Register(u8), + Immediate(i32), +} + +impl FromStr for Operand { + type Err = (); + fn from_str(s: &str) -> Result<Self, ()> { + match s { + "a" => Ok(Operand::Register(0)), + "b" => Ok(Operand::Register(1)), + "c" => Ok(Operand::Register(2)), + "d" => Ok(Operand::Register(3)), + _ => Ok(Operand::Immediate(s.parse().map_err(|_| ())?)), + } + } +} + +#[derive(Clone, Copy)] +enum Operation { + Cpy(Operand, Operand), + Inc(Operand), + Dec(Operand), + Jnz(Operand, Operand), +} + +impl FromStr for Operation { + type Err = (); + fn from_str(s: &str) -> Result<Self, ()> { + let mut iter = s.split(' '); + match iter.next() { + Some("cpy") => { + let src = iter.next().ok_or(())?.parse()?; + let dest = iter.next().ok_or(())?.parse()?; + Ok(Operation::Cpy(src, dest)) + }, + Some("inc") => Ok(Operation::Inc(iter.next().ok_or(())?.parse()?)), + Some("dec") => Ok(Operation::Dec(iter.next().ok_or(())?.parse()?)), + Some("jnz") => { + let cond = iter.next().ok_or(())?.parse()?; + let jump = iter.next().ok_or(())?.parse()?; + Ok(Operation::Jnz(cond, jump)) + }, + _ => Err(()), + } + } +} + +#[derive(Default)] +struct Vm { + registers: [i32; 4], + operations: Vec<Operation>, + index: i32, +} + +impl FromStr for Vm { + type Err = (); + fn from_str(s: &str) -> Result<Self, ()> { + let mut vm = Self::default(); + for line in s.lines() { + vm.operations.push(line.parse()?); + } + Ok(vm) + } +} + +impl Vm { + fn step(&mut self) -> bool { + match self.operations[self.index as usize] { + Operation::Cpy(Operand::Immediate(imm), Operand::Register(reg)) => { + self.registers[reg as usize] = imm; + self.index += 1; + }, + Operation::Cpy(Operand::Register(src), Operand::Register(dest)) => { + self.registers[dest as usize] = self.registers[src as usize]; + self.index += 1; + }, + Operation::Inc(Operand::Register(reg)) => { + self.registers[reg as usize] += 1; + self.index += 1; + }, + Operation::Dec(Operand::Register(reg)) => { + self.registers[reg as usize] -= 1; + self.index += 1; + }, + Operation::Jnz(Operand::Immediate(cond), Operand::Immediate(jump)) => { + if cond != 0 { + self.index += jump; + } else { + self.index += 1; + } + }, + Operation::Jnz(Operand::Register(reg), Operand::Immediate(jump)) => { + if self.registers[reg as usize] != 0 { + self.index += jump; + } else { + self.index += 1; + } + }, + _ => panic!("invalid operation"), + } + + (self.index as usize) < self.operations.len() + } +} + +fn solve(input: &str) -> i32 { + let mut vm: Vm = input.parse().unwrap(); + while vm.step() { } + vm.registers[0] +} + +fn main() { + let mut input = String::new(); + io::stdin().read_to_string(&mut input).unwrap(); + + println!("Part 1: {}", solve(&input)); +} + +#[test] +fn part1() { + let input = " +cpy 41 a +inc a +inc a +dec a +jnz a 2 +dec a +"; + assert_eq!(42, solve(input.trim())); +} |