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#include <filesystem>
#include <fstream>
#include <iostream>
#include <map>
#include <optional>
#include <sstream>
#include <string>
#include <utility>
#include <vector>
using namespace std;
namespace {
enum class OpCode : uint8_t {
CPY,
INC,
DEC,
JNZ,
OUT,
};
using memory_type = map<char, int>;
struct Argument {
explicit Argument(string value)
: value{ std::move(value) }
{
}
[[nodiscard]]
int eval(const memory_type& memory) const
{
const auto chr = value.at(0);
if ( chr >= 'a' && chr <= 'z' ) {
return memory.at(chr);
}
else {
return stoi(value);
}
}
[[nodiscard]]
char reg() const
{
if ( !is_reg() ) {
throw runtime_error("invalid register access! "s + value);
}
return value.at(0);
}
[[nodiscard]]
bool is_reg() const
{
const auto chr = value.at(0);
return chr >= 'a' && chr <= 'z';
}
string value;
};
struct Instruction {
Instruction(OpCode opCode, const Argument& x)
: opCode{ opCode }
, x{ x }
{
}
Instruction(OpCode opCode, const Argument& x, const Argument& y)
: opCode{ opCode }
, x{ x }
, y{ y }
{
}
OpCode opCode;
optional<Argument> x;
optional<Argument> y;
};
vector<string>
split_words(const string& line, char sep = ' ')
{
vector<string> words;
stringstream strm{ line };
for ( string word; getline(strm, word, sep); ) {
words.emplace_back(word);
}
return words;
}
vector<Instruction>
read_file(const filesystem::path& filename)
{
ifstream input{ filename };
vector<Instruction> instructions;
for ( string line; getline(input, line); ) {
const auto words = split_words(line);
if ( words.at(0) == "cpy" ) {
instructions.emplace_back(OpCode::CPY, Argument(words.at(1)), Argument(words.at(2)));
}
else if ( words.at(0) == "inc" ) {
instructions.emplace_back(OpCode::INC, Argument(words.at(1)));
}
else if ( words.at(0) == "dec" ) {
instructions.emplace_back(OpCode::DEC, Argument(words.at(1)));
}
else if ( words.at(0) == "jnz" ) {
instructions.emplace_back(OpCode::JNZ, Argument(words.at(1)), Argument(words.at(2)));
}
else if ( words.at(0) == "out" ) {
instructions.emplace_back(OpCode::OUT, Argument(words.at(1)));
}
else {
cerr << "unknown opcode..." << '\n';
}
}
return instructions;
}
#define JIT
string
execute(memory_type& memory, vector<Instruction> instructions)
{
string result;
for ( size_t ip = 0; ip < instructions.size(); ) {
const auto& instruction = instructions.at(ip);
// cout << "#" << ip << " - " << memory['a'] << ", " << memory['b'] << ", " << memory['c'] << ", " << memory['d'] << ": " << (int) instruction.opCode << '\n';
switch ( instruction.opCode ) {
using enum OpCode;
case CPY:
memory[instruction.y->reg()] = instruction.x->eval(memory);
++ip;
break;
case INC:
memory[instruction.x->reg()]++;
++ip;
break;
case DEC:
memory[instruction.x->reg()]--;
++ip;
break;
case JNZ:
if ( instruction.x->eval(memory) != 0 ) {
ip += static_cast<size_t>(instruction.y->eval(memory));
}
else {
++ip;
}
break;
case OUT:
result += to_string(instruction.x->eval(memory));
if ( result.size() >= 20 ) {
ip = instructions.size();
}
else {
++ip;
}
}
}
return result;
}
void
part1(const vector<Instruction>& instructions)
{
for ( int seed = 0;; ++seed ) {
map<char, int> memory;
memory['a'] = seed;
memory['b'] = 0;
memory['c'] = 0;
memory['d'] = 0;
auto result = execute(memory, instructions);
if ( result == "01010101010101010101" ) {
cout << "Part1: " << seed << '\n';
return;
}
}
}
} // namespace
int
main()
{
const auto instructions = read_file("data/day25.txt");
try {
part1(instructions);
}
catch ( exception& e ) {
cerr << e.what() << '\n';
}
}
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