diff --git a/12/CMakeLists.txt b/12/CMakeLists.txt
new file mode 100644
index 0000000..6f09420
--- /dev/null
+++ b/12/CMakeLists.txt
@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.10)
+set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD_REQUIRED True)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+enable_language(CXX)
+
+project(AoC12)
+
+if(APPLE)
+    include_directories(/usr/local/include)
+    link_directories(/usr/local/lib)
+endif()
+
+if(WIN32)
+	add_executable(${CMAKE_PROJECT_NAME} WIN32)
+else()
+	add_executable(${CMAKE_PROJECT_NAME})
+endif()
+
+target_sources(${CMAKE_PROJECT_NAME}
+	PRIVATE main.cpp
+	)
diff --git a/12/input b/12/input
new file mode 100644
index 0000000..262ee68
--- /dev/null
+++ b/12/input
@@ -0,0 +1,19 @@
+lg-GW
+pt-start
+pt-uq
+nx-lg
+ve-GW
+start-nx
+GW-start
+GW-nx
+pt-SM
+sx-GW
+lg-end
+nx-SM
+lg-SM
+pt-nx
+end-ve
+ve-SM
+TG-uq
+end-SM
+SM-uq
diff --git a/12/main.cpp b/12/main.cpp
new file mode 100644
index 0000000..9feaa17
--- /dev/null
+++ b/12/main.cpp
@@ -0,0 +1,105 @@
+#include <algorithm>
+#include <deque>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+using GraphMap = std::unordered_map<std::string, std::vector<std::string>>;
+
+GraphMap getMap(const std::string &file_name) {
+    GraphMap map{};
+
+    std::ifstream file(file_name);
+    std::string str;
+    while (std::getline(file, str)) {
+        auto deliminer = str.find_first_of('-');
+        auto start = str.substr(0, deliminer);
+        auto end = str.substr(deliminer + 1);
+        map[start].push_back(end);
+        map[end].push_back(start);
+    }
+    return map;
+}
+
+uint64_t getPaths(const GraphMap &map, const std::string &start,
+                  std::vector<std::string> &visited,
+#ifdef DEBUG
+                  std::vector<std::string> &path,
+#endif
+                  bool can_twice = false, bool has_twice = false) {
+    uint64_t paths = 0;
+    for (const auto &dest : map.at(start)) {
+        if (dest == "start") {
+            continue;
+        }
+        bool is_twice = false;
+        if (std::find(visited.begin(), visited.end(), dest) != visited.end()) {
+            if (!can_twice || (can_twice && has_twice)) {
+                continue;
+            }
+            has_twice = true;
+            is_twice = true;
+        }
+        if (dest == "end") {
+            paths++;
+#ifdef DEBUG
+            for (auto &thingy : path) {
+                std::cout << thingy << "->";
+            }
+            std::cout << "end" << std::endl;
+#endif
+            continue;
+        }
+        if (dest[0] >= 'a' && dest[0] <= 'z' && !is_twice) {
+            visited.push_back(dest);
+        }
+#ifdef DEBUG
+        path.push_back(dest);
+        paths += getPaths(map, dest, visited, path, can_twice, has_twice);
+        path.pop_back();
+#endif
+        paths += getPaths(map, dest, visited, can_twice, has_twice);
+        if (dest[0] >= 'a' && dest[0] <= 'z' && !is_twice) {
+            visited.pop_back();
+        }
+        if (is_twice) {
+            has_twice = false;
+        }
+    }
+    return paths;
+}
+
+uint64_t part1(const GraphMap &map) {
+    std::vector<std::string> visited{ "start" };
+#ifdef DEBUG
+    std::vector<std::string> path{ "start" };
+    return getPaths(map, "start", visited, path);
+#endif
+    return getPaths(map, "start", visited);
+}
+
+uint64_t part2(const GraphMap &map) {
+    std::vector<std::string> visited{ "start" };
+#ifdef DEBUG
+    std::vector<std::string> path{ "start" };
+    return getPaths(map, "start", visited, path, true);
+#endif
+    return getPaths(map, "start", visited, true);
+}
+
+int main(int argc, char **argv) {
+    if (argc < 2) {
+        std::cerr << "You must provide input file!" << std::endl;
+        return 1;
+    }
+    auto map = getMap(argv[1]);
+    std::cout << "There are \033[91;1m" << part1(map)
+              << "\033[0m paths in the cave system." << std::endl;
+    std::cout << "There are \033[91;1m" << part2(map)
+              << "\033[0m paths in the cave system with new rules."
+              << std::endl;
+    return 0;
+}