Simulate a Least Recently Used (LRU) cache and return the results of get operations. Evictions remove the least-recently-used entry.

An LRU cache is a fixed-capacity key-value store commonly used in web servers, databases, and mobile apps to keep frequently accessed items in memory. When the cache is full and a new item is inserted, the item that hasn't been used for the longest time is evicted. get(key) reads a value (and marks it as most recently used); put(key, value) inserts or updates a value.