day25 - part 1

CMakeLists.txt

@@ -113,6 +113,6 @@ add_executable(day24 src/day24.cc)
 target_compile_features(day24 PRIVATE cxx_std_20)
 target_link_libraries(day24 PRIVATE ${FMT_LIBRARIES})
 
-# add_executable(day25 src/day25.cc)
-# target_compile_features(day25 PRIVATE cxx_std_20)
-# target_link_libraries(day25 PRIVATE ${FMT_LIBRARIES})
+add_executable(day25 src/day25.cc)
+target_compile_features(day25 PRIVATE cxx_std_20)
+target_link_libraries(day25 PRIVATE ${FMT_LIBRARIES})

adventofcode.com_2016_day_25_input.txt

@@ -0,0 +1,30 @@
+cpy a d
+cpy 4 c
+cpy 633 b
+inc d
+dec b
+jnz b -2
+dec c
+jnz c -5
+cpy d a
+jnz 0 0
+cpy a b
+cpy 0 a
+cpy 2 c
+jnz b 2
+jnz 1 6
+dec b
+dec c
+jnz c -4
+inc a
+jnz 1 -7
+cpy 2 b
+jnz c 2
+jnz 1 4
+dec b
+dec c
+jnz 1 -4
+jnz 0 0
+out b
+jnz a -19
+jnz 1 -21

src/day25.cc

@@ -0,0 +1,237 @@
+#include <boost/algorithm/string/classification.hpp>
+#include <boost/algorithm/string/split.hpp>
+
+#include <array>
+#include <cstddef>
+#include <cstdlib>
+#include <fmt/core.h>
+#include <iostream>
+#include <iterator>
+#include <limits>
+#include <map>
+#include <string>
+#include <string_view>
+#include <type_traits>
+#include <variant>
+#include <vector>
+
+enum class Register
+{
+    A = 0,
+    B,
+    C,
+    D,
+};
+
+enum class Op
+{
+    NOP = 0,
+    CPY,
+    INC,
+    DEC,
+    JNZ,
+    OUT,
+};
+
+using Argument = std::variant<bool, Register, int64_t>;
+
+struct Instruction {
+    Op op = Op::NOP;
+    Argument arg1;
+    Argument arg2;
+    bool dump_regs = false;
+};
+
+using Program = std::vector<Instruction>;
+
+static constexpr const unsigned MAX_OUTPUT = 12;
+
+struct CPU
+{
+    CPU(Program const& p) noexcept
+        : program {p}
+    { }
+
+    void run() noexcept;
+
+    constexpr int64_t& get_value(Argument const& arg) noexcept {
+        return std::visit(
+            [this](auto&& _arg) -> int64_t& {
+                using T = std::decay_t<decltype(_arg)>;
+                if constexpr (std::is_same_v<T, int64_t>) {
+                    tmp1 = _arg;
+                    return tmp1;
+                } else if constexpr (std::is_same_v<T, Register>) {
+                    return registers.at(static_cast<unsigned>(_arg));
+                } else {
+                    assert(false);
+                }
+            },
+            arg);
+    }
+
+    Program const& program;
+    std::array<int64_t, sizeof(Register)> registers = {0};
+    std::string output;
+    int64_t tmp1 = 0;
+};
+
+
+void CPU::run() noexcept
+{
+    output.clear();
+
+    for (auto pc = program.begin(); pc != program.end();)
+    {
+        Instruction const& i = *pc;
+
+        if (i.dump_regs) {
+            fmt::print(
+                "A: {}; B: {}; C: {}; D:{}\n",
+                registers.at(static_cast<unsigned>(Register::A)),
+                registers.at(static_cast<unsigned>(Register::B)),
+                registers.at(static_cast<unsigned>(Register::C)),
+                registers.at(static_cast<unsigned>(Register::D)));
+        }
+
+        switch(i.op) {
+        case Op::INC:
+            get_value(i.arg1) += 1;
+            ++pc;
+            break;
+        case Op::DEC:
+            get_value(i.arg1) -= 1;
+            ++pc;
+            break;
+        case Op::CPY:
+            get_value(i.arg2) = get_value(i.arg1);
+            ++pc;
+            break;
+        case Op::JNZ:
+            if (get_value(i.arg1)) {
+                std::advance(pc, get_value(i.arg2));
+            } else {
+                ++pc;
+            }
+            break;
+        case Op::OUT:
+            output.push_back(get_value(i.arg1) == 1 ? '1' : '0');
+            if (output.size() == MAX_OUTPUT) {
+                pc = program.end();
+            } else {
+                ++pc;
+            }
+            break;
+        default:
+            assert(false);
+        }
+    }
+}
+
+
+int main()
+{
+    Program prog;
+
+    std::string line;
+    while(std::getline(std::cin, line))
+    {
+        if (line.empty()) break;
+
+        static const std::map<std::string, Op> str2op = {
+            {"cpy", Op::CPY}, {"inc", Op::INC}, {"dec", Op::DEC}, {"jnz", Op::JNZ}, {"out", Op::OUT}};
+
+        auto is_reg = [](std::string_view const s) -> bool {
+            return (s.size() == 1 && (s.at(0) == 'a' || s.at(0) == 'b' || s.at(0) == 'c' || s.at(0) == 'd'));
+        };
+        auto str2reg = [](std::string_view const s) -> Register {
+            const unsigned char c = s.at(0);
+            switch (c) {
+            case 'a': return Register::A;
+            case 'b': return Register::B;
+            case 'c': return Register::C;
+            case 'd': return Register::D;
+            default: assert(false);
+            }
+        };
+
+        std::vector<std::string> parts;
+        boost::algorithm::split(parts, line, boost::algorithm::is_any_of(" "));
+        assert(parts.size() > 1);
+
+        Instruction i = {};
+        if (parts.at(0) == "!") {
+            i.dump_regs = true;
+            parts.erase(parts.begin());
+        }
+        i.op = str2op.at(parts.at(0));
+        switch(i.op) {
+        case Op::INC:
+            assert(parts.size() == 2);
+            i.arg1 = str2reg(parts.at(1));
+            break;
+        case Op::DEC:
+            assert(parts.size() == 2);
+            i.arg1 = str2reg(parts.at(1));
+            break;
+        case Op::CPY:
+            assert(parts.size() == 3);
+            if (is_reg(parts.at(1))) {
+                i.arg1 = str2reg(parts.at(1));
+            } else {
+                i.arg1 = std::stoll(parts.at(1));
+            }
+            if (is_reg(parts.at(2))) {
+                i.arg2 = str2reg(parts.at(2));
+            } else {
+                i.arg2 = std::stoll(parts.at(2));
+            }
+            break;
+        case Op::JNZ:
+            assert(parts.size() == 3);
+            if (is_reg(parts.at(1))) {
+                i.arg1 = str2reg(parts.at(1));
+            } else {
+                i.arg1 = std::stoll(parts.at(1));
+            }
+            if (is_reg(parts.at(2))) {
+                i.arg2 = str2reg(parts.at(2));
+            } else {
+                i.arg2 = std::stoll(parts.at(2));
+            }
+            break;
+        case Op::OUT:
+            assert(parts.size() == 2);
+            i.arg1 = str2reg(parts.at(1));
+            break;
+        default: assert(false);
+        }
+        prog.push_back(std::move(i));
+    }
+
+
+    const std::string target = []() {
+        std::string ret;
+        unsigned char c = '0';
+        for (unsigned i =0; i<MAX_OUTPUT; ++i) {
+            ret += c;
+            c = (c == '0' ? '1' : '0');
+        }
+        return ret;
+    }();
+
+    {
+            CPU cpu1(prog);
+            for (unsigned x = 0; x < -1; ++x) {
+                cpu1.registers = {0};
+                cpu1.registers.at(static_cast<unsigned>(Register::A)) = x;
+                cpu1.run();
+                if (cpu1.output == target) {
+                    fmt::print("1: {} ({})\n", x, cpu1.output);
+                    break;
+                }
+            }
+    }
+
+    return 0;
+}