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use std::io;
use std::io::BufRead;
#[derive(Copy, Clone)]
enum Opcode {
Addr, Addi,
Mulr, Muli,
Banr, Bani,
Borr, Bori,
Setr, Seti,
Gtir, Gtri, Gtrr,
Eqir, Eqri, Eqrr,
}
impl Opcode {
fn from_id(id: u16) -> Opcode {
use self::Opcode::*;
static VALUES: [Opcode; 16] = [Addr, Addi, Mulr, Muli, Banr, Bani, Borr, Bori, Setr, Seti, Gtir, Gtri, Gtrr, Eqir, Eqri, Eqrr];
VALUES[id as usize]
}
}
struct Instr {
op: usize,
a: usize,
b: usize,
c: usize,
}
impl Instr {
fn from(line: &str) -> Self {
let mut iter = line.split(' ').map(|s| s.parse().unwrap());
let op = iter.next().unwrap();
let a = iter.next().unwrap();
let b = iter.next().unwrap();
let c = iter.next().unwrap();
Instr { op, a, b, c }
}
}
#[derive(PartialEq, Eq, Clone)]
struct Machine {
regs: [usize; 4],
}
impl Machine {
fn from(line: &str) -> Self {
let mut machine = Machine { regs: [0; 4] };
let mut i = 0;
for num in line.split(", ").map(|s| s.parse().unwrap()) {
machine.regs[i] = num;
i += 1;
}
machine
}
fn exec(&mut self, op: Opcode, a: usize, b: usize, c: usize) {
match op {
Opcode::Addr => self.regs[c] = self.regs[a] + self.regs[b],
Opcode::Addi => self.regs[c] = self.regs[a] + b,
Opcode::Mulr => self.regs[c] = self.regs[a] * self.regs[b],
Opcode::Muli => self.regs[c] = self.regs[a] * b,
Opcode::Banr => self.regs[c] = self.regs[a] & self.regs[b],
Opcode::Bani => self.regs[c] = self.regs[a] & b,
Opcode::Borr => self.regs[c] = self.regs[a] | self.regs[b],
Opcode::Bori => self.regs[c] = self.regs[a] | b,
Opcode::Setr => self.regs[c] = self.regs[a],
Opcode::Seti => self.regs[c] = a,
Opcode::Gtir => self.regs[c] = if a > self.regs[b] { 1 } else { 0 },
Opcode::Gtri => self.regs[c] = if self.regs[a] > b { 1 } else { 0 },
Opcode::Gtrr => self.regs[c] = if self.regs[a] > self.regs[b] { 1 } else { 0 },
Opcode::Eqir => self.regs[c] = if a == self.regs[b] { 1 } else { 0 },
Opcode::Eqri => self.regs[c] = if self.regs[a] == b { 1 } else { 0 },
Opcode::Eqrr => self.regs[c] = if self.regs[a] == self.regs[b] { 1 } else { 0 },
}
}
}
struct Sample {
before: Machine,
after: Machine,
instr: Instr,
}
impl Sample {
fn behaves_as(&self) -> u16 {
let mut r = 0;
for id in 0..16 {
let op = Opcode::from_id(id);
let mut m = self.before.clone();
m.exec(op, self.instr.a, self.instr.b, self.instr.c);
if m == self.after {
r |= 1 << id;
}
}
r
}
}
fn parse_input<T: BufRead>(reader: T) -> io::Result<(Vec<Sample>, Vec<Instr>)> {
let mut line_iter = reader.lines();
let mut samples = Vec::new();
let program;
loop {
let line = line_iter.next().unwrap()?;
if line.len() == 0 {
line_iter.next();
program = line_iter.map(|l| Instr::from(&l.unwrap())).collect::<Vec<_>>();
break;
} else if &line[..1] == "B" {
let before = Machine::from(&line[9..line.len()-1]);
let line = line_iter.next().unwrap()?;
let instr = Instr::from(&line);
let line = line_iter.next().unwrap()?;
let after = Machine::from(&line[9..line.len()-1]);
samples.push(Sample { before, after, instr });
line_iter.next();
} else {
assert!(false);
}
}
Ok((samples, program))
}
fn resolve_helper(masks: &[u16; 16], res: &mut [u16; 16], at: usize, available: u16) -> bool {
if at == 16 {
return true;
}
let mut walker = available;
while walker != 0 {
let n = walker.trailing_zeros();
let bit = 1 << n;
walker &= !bit;
if (masks[at] & bit) != 0 {
res[at] = n as u16;
if resolve_helper(masks, res, at + 1, available & !bit) {
return true;
}
}
}
false
}
fn resolve_mapping(masks: &[u16; 16]) -> [u16; 16] {
let mut res = [0; 16];
assert!(resolve_helper(masks, &mut res, 0, 0xffff));
res
}
pub fn main<T: BufRead>(reader: T) -> io::Result<(String, String)> {
let (samples, program) = parse_input(reader)?;
let mut num_geq_3 = 0;
let mut code_masks = [0xffff; 16];
for sample in samples {
let mask = sample.behaves_as();
if mask.count_ones() >= 3 {
num_geq_3 += 1;
}
code_masks[sample.instr.op] &= mask;
}
let part1 = num_geq_3;
let mapping = resolve_mapping(&code_masks);
let mut m = Machine { regs: [0; 4] };
for instr in program {
m.exec(Opcode::from_id(mapping[instr.op]), instr.a, instr.b, instr.c);
}
let part2 = m.regs[0];
Ok((part1.to_string(), part2.to_string()))
}
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