1 files changed, 266 insertions, 0 deletions

diff --git a/2017/src/day18.cpp b/2017/src/day18.cpp
new file mode 100644
index 0000000..bfdd7e3
--- /dev/null
+++ b/2017/src/day18.cpp
@@ -0,0 +1,266 @@
+#include <charconv>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <queue>
+#include <sstream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+template<typename T>
+struct CPU {
+        [[nodiscard]]
+        T get(const string& ref)
+        {
+                T value{};
+                auto [ptr, ec] = from_chars(ref.data(), ref.data() + ref.size(), value);
+
+                if ( ec == errc() ) {
+                        return value;
+                }
+
+                return memory[ref];
+        }
+
+        void set(const string& ref, T value)
+        {
+                memory[ref] = value;
+        }
+
+        void add(const string& ref, T value)
+        {
+                memory[ref] += value;
+        }
+
+        void mul(const string& ref, T value)
+        {
+                memory[ref] *= value;
+        }
+
+        void mod(const string& ref, T value)
+        {
+                memory[ref] %= value;
+        }
+
+        T execute(const vector<vector<string>>& code)
+        {
+                long played_sound{};
+
+                for ( size_t ip = 0; ip < code.size(); ++ip ) {
+                        const auto& line   = code.at(ip);
+                        const auto& opcode = line.at(0);
+
+                        if ( opcode == "snd" ) {
+                                played_sound = get(line.at(1));
+                        }
+                        else if ( opcode == "rcv" ) {
+                                auto value = get(line.at(1));
+                                if ( value != 0 ) {
+                                        return played_sound;
+                                }
+                        }
+                        else if ( opcode == "set" ) {
+                                set(line.at(1), get(line.at(2)));
+                        }
+                        else if ( opcode == "add" ) {
+                                add(line.at(1), get(line.at(2)));
+                        }
+                        else if ( opcode == "mul" ) {
+                                mul(line.at(1), get(line.at(2)));
+                        }
+                        else if ( opcode == "mod" ) {
+                                mod(line.at(1), get(line.at(2)));
+                        }
+                        else if ( opcode == "jgz" ) {
+                                auto value = get(line.at(1));
+                                if ( value > 0 ) {
+                                        auto offset = get(line.at(2));
+                                        ip += static_cast<size_t>(offset - 1);
+                                }
+                        }
+                        else {
+                                cerr << "unknown opcode: " << opcode << '\n';
+                                return -1;
+                        }
+                }
+                return -1;
+        }
+
+        map<string, T> memory;
+};
+
+template<typename T>
+struct CPU2 {
+        CPU2(queue<T>& in, queue<T>& out)
+            : in{ in }
+            , out{ out }
+        {
+        }
+
+        [[nodiscard]]
+        T get(const string& ref)
+        {
+                T value{};
+                auto [ptr, ec] = from_chars(ref.data(), ref.data() + ref.size(), value);
+
+                if ( ec == errc() ) {
+                        return value;
+                }
+
+                return memory[ref];
+        }
+
+        void set(const string& ref, T value)
+        {
+                memory[ref] = value;
+        }
+
+        void add(const string& ref, T value)
+        {
+                memory[ref] += value;
+        }
+
+        void mul(const string& ref, T value)
+        {
+                memory[ref] *= value;
+        }
+
+        void mod(const string& ref, T value)
+        {
+                memory[ref] %= value;
+        }
+
+        bool step(const vector<vector<string>>& code)
+        {
+                if ( ip >= code.size() ) {
+                        return false;
+                }
+
+                const auto& line   = code.at(ip);
+                const auto& opcode = line.at(0);
+
+                if ( opcode == "snd" ) {
+                        out.push(get(line.at(1)));
+                        ++send_count;
+                }
+                else if ( opcode == "rcv" ) {
+                        if ( in.empty() ) {
+                                waiting = true;
+                                return true;
+                        }
+                        else {
+                                auto value = in.front();
+                                in.pop();
+                                set(line.at(1), value);
+                                waiting = false;
+                        }
+                }
+                else if ( opcode == "set" ) {
+                        set(line.at(1), get(line.at(2)));
+                }
+                else if ( opcode == "add" ) {
+                        add(line.at(1), get(line.at(2)));
+                }
+                else if ( opcode == "mul" ) {
+                        mul(line.at(1), get(line.at(2)));
+                }
+                else if ( opcode == "mod" ) {
+                        mod(line.at(1), get(line.at(2)));
+                }
+                else if ( opcode == "jgz" ) {
+                        auto value = get(line.at(1));
+                        if ( value > 0 ) {
+                                auto offset = get(line.at(2));
+                                ip += static_cast<size_t>(offset);
+                                return true;
+                        }
+                }
+                else {
+                        cerr << "unknown opcode: " << opcode << '\n';
+                        return false;
+                }
+
+                ++ip;
+
+                return true;
+        }
+
+        size_t         ip{};
+        queue<T>&      in;
+        queue<T>&      out;
+        bool           waiting{ false };
+        T              send_count{};
+        map<string, T> memory;
+};
+
+vector<string>
+split(const string& line)
+{
+        stringstream   strm{ line };
+        vector<string> data;
+
+        for ( string line; strm >> line; ) {
+                data.emplace_back(line);
+        }
+
+        return data;
+}
+
+vector<vector<string>>
+read_file(const filesystem::path& filename)
+{
+        ifstream               file{ filename };
+        vector<vector<string>> data;
+
+        for ( string line; getline(file, line); ) {
+                const auto parts = split(line);
+                data.emplace_back(parts);
+        }
+
+        return data;
+}
+
+void
+part1(const vector<vector<string>>& code)
+{
+        CPU<long> cpu{};
+
+        cout << "Part1: " << cpu.execute(code) << '\n';
+}
+
+void
+part2(const vector<vector<string>>& code)
+{
+        queue<long> queue1;
+        queue<long> queue2;
+        CPU2<long>  cpu1{ queue1, queue2 };
+        CPU2<long>  cpu2{ queue2, queue1 };
+
+        cpu1.set("p", 0);
+        cpu2.set("p", 1);
+
+        for ( ;; ) {
+                auto cpu1_running = cpu1.step(code);
+                auto cpu2_running = cpu2.step(code);
+
+                if ( (cpu1.waiting || !cpu1_running) && (cpu2.waiting || !cpu2_running) ) {
+                        break;
+                }
+        }
+        cout << "Part2: " << cpu2.send_count << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        auto instr = read_file("data/day18.txt");
+        part1(instr);
+        part2(instr);
+}