Implement an in-memory key-value cache with least-recently-used eviction and per-entry expiration. The cache has a fixed positive `capacity`. Each inserted key has a time-to-live value. Once an entry expires, it should behave as if it does not exist and should be removed from the cache when encountered. Design a class with the following operations: ```text ExpiringCache(int capacity) int get(int key, int now) void put(int key, int value, int ttl, int now) ``` Rules: - `put(key, value, ttl, now)` inserts or updates `key` with `value`. - The entry expires at time `now + ttl`. - `get(key, now)` returns the value if the key exists and has not expired; otherwise return `-1`. - Accessing a non-expired key through `get` makes it the most recently used entry. - Updating an existing non-expired key through `put` updates its value, expiration time, and recency. - If an existing key has already expired, treat the operation as inserting a new key. - If inserting a new entry causes the number of non-expired entries to exceed `capacity`, evict the least recently used non-expired entry. - Expired entries should be deleted when detected. Target: make `get` and `put` run in `O(1)` average time, using an appropriate combination of a hash map and a doubly linked list.