Redis List

Redis's LIST type is a doubly linked list under the hood, which is what makes push and pop at both ends O(1). You will build a small version of it.

Implement the RedisList class backed by a doubly linked list (a Python list/deque or C++ vector/deque defeats the purpose — the point is to manage the nodes yourself):

• lpush(self, values: list) -> int — push each value onto the head (left), one at a time in the given order, and return the new length. lpush(["a", "b", "c"]) leaves the list as c, b, a.
• rpush(self, values: list) -> int — push each value onto the tail (right), one at a time, and return the new length.
• lpop(self, count: int = 1) -> list — remove up to count values from the head and return them in pop order. If the list has fewer than count elements, return everything. On an empty list return [].
• rpop(self, count: int = 1) -> list — same, from the tail.

All four operations must be O(1) per element (O(count) for a pop of count items).

Example:

lpush(["a", "b", "c"]) → 3 (list is now c, b, a) rpush(["d", "e"]) → 5 (list is now c, b, a, d, e) lpop(2) → ["c", "b"] (list is now a, d, e) rpop(1) → ["e"] (list is now a, d)

Constraints:

• Values are strings
• count >= 1
• Popping more than the list holds returns only what is available (never raises)
• Must use an explicit doubly linked list with head and tail pointers