LeetCode #146 - LRU Cache\nDesign and implement a data structure that allows you to add key-value pairs and retrieve the value of a given key. If the key does not exist, return -1. If the cache reaches its capacity, it should invalidate the least recently used item before inserting a new item.\nInput: An integer capacity and a list of operations in the format ['put(key, value)', 'get(key)', ...]\nOutput: Return the result of get operations in order.\nConstraints: 1 <= capacity <= 3000 and all keys are unique.

``` class LRUCache:\n def __init__(self, capacity: int):\n self.capacity = capacity\n self.cache = {}\n self.order = []\n def get(self, key: int) -> int:\n if key in self.cache:\n self.order.remove(key)\n self.order.append(key)\n return self.cache[key]\n return -1\n def put(self, key: int, value: int) -> None:\n if key in self.cache:\n self.order.remove(key)\n elif len(self.cache) >= self.capacity:\n lru_key = self.order.pop(0)\n del self.cache[lru_key]\n self.cache[key] = value\n self.order.append(key) ```