Added LRU Cache

CMakeLists.txt

@@ -722,4 +722,15 @@ add_executable(PartitionList
 target_link_libraries(
         PartitionList
         GTest::gtest_main
+)
+
+# LRU Cache
+add_executable(LRUCache
+        Medium/LRUCache/include/solution.hpp
+        Medium/LRUCache/tests/test.cpp
+)
+
+target_link_libraries(
+        LRUCache
+        GTest::gtest_main
 )

Medium/LRUCache/include/solution.hpp

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <list>
+#include <iostream>
+#include <algorithm>
+#include <gtest/gtest.h>
+
+class LRUCache {
+public:
+    explicit LRUCache(std::size_t capacity) : _cache_size(capacity) { };
+
+    auto get(int32_t key) -> int32_t {
+        if (_pair.find(key) != _pair.end()) {
+            _doubly_list.splice(_doubly_list.begin(),
+                                _doubly_list, _pair[key]);
+            return _pair[key]->second;
+        }
+
+        return -1;
+    }
+
+    auto put(int32_t key, int32_t value) -> void {
+        if (_pair.find(key) != _pair.end()) {
+            _pair[key]->second = value;
+            _doubly_list.splice(_doubly_list.begin(),
+                                _doubly_list, _pair[key]);
+            return;
+        }
+
+        _doubly_list.emplace_front(key, value);
+        _pair[key] = _doubly_list.begin();
+
+        if (_doubly_list.size() > _cache_size) {
+            std::pair<int32_t, int32_t> &back = _doubly_list.back();
+            _pair.erase(back.first);
+            _doubly_list.pop_back();
+        }
+    }
+
+private:
+    std::size_t _cache_size;
+    std::list<std::pair<int32_t, int32_t>> _doubly_list;
+    std::unordered_map<int32_t, std::list<std::pair<int32_t, int32_t>>::iterator> _pair;
+};

Medium/LRUCache/tests/test.cpp

@@ -0,0 +1,17 @@
+#include "../include/solution.hpp"
+
+auto main() -> int {
+    auto *cache = new LRUCache(2);
+    cache->put(1, 1);
+    cache->put(2, 2);
+    std::cout << cache->get(1) << '\n';
+    cache->put(3, 3);
+    std::cout << cache->get(2) << '\n';
+    cache->put(4, 4);
+    std::cout << cache->get(1) << '\n';
+    std::cout << cache->get(3) << '\n';
+    std::cout << cache->get(4) << '\n';
+    delete cache;
+
+    return 0;
+}