LRU Cache

Process operations on a least recently used cache with fixed positive capacity. The cache starts empty.
put has arguments [key, value]. Insert or update the key and make it most recently used. If a new key makes the cache exceed capacity, evict the least recently used key. A put produces no result.
get has arguments [key]. Return its value and make the key most recently used, or return -1 when the key is absent.
Return the results of all get operations in operation order.

Function
runLruCache(capacity: int, operations: String[], arguments: int[][]) → int[]

Examples
Example 1
capacity = 2
operations = ["put","put","get","put","get","get"]
arguments = [[1,1],[2,2],[1],[3,3],[2],[3]]
return = [1,-1,3]
Reading key 1 makes it recent. Inserting key 3 then evicts key 2.
Example 2
capacity = 1
operations = ["put","put","get","put","get"]
arguments = [[5,10],[5,20],[5],[6,30],[5]]
return = [20,-1]
Updating key 5 changes its value without eviction. Inserting key 6 later evicts key 5.
Example 3
capacity = 2
operations = ["get","put","get","get"]
arguments = [[7],[7,70],[7],[7]]
return = [-1,70,70]
The first read misses. After insertion, repeated successful reads return 70 and preserve recency.

Constraints
1 <= capacity <= 10^5
1 <= operations.length = arguments.length <= 2 * 10^5
Each operation is exactly get or put.
A get row has one integer; a put row has two integers.
0 <= key, value <= 10^9
Every operation must run in average O(1) time.

The trick is pairing a hash map with a doubly linked list. The map takes a key to its list node, so lookup is O(1). The list holds recency order, with the most recent at one end and the least recent at the other. On get, move the node to the front. On put, update and move if the key exists, otherwise insert at the front and evict the tail when size passes capacity. Use dummy head and tail nodes so you never branch on null. The common pitfalls are forgetting that put on an existing key also refreshes recency, forgetting to delete the evicted key from the map, and skipping the -1 on a miss. Here you only collect results from get calls, so don't append anything for put. In a JS or Python OA, an ordered dictionary shortcut works, but the constraint says average O(1), so know the manual version. If you freeze, StealthCoder can feed you the node-splice code live.

The honest play: practice the pattern, and have StealthCoder ready for the one you didn't see coming.