Design a Set of Stacks (Capacity Limit)

To solve this, I first visualize the problem as a collection of fixed-size containers. I would implement a class containing a list of stack instances. For the push operation, I check if the current last stack has reached its capacity threshold. If it has, I instantiate a new stack object and append it to my list, then push the item onto this new stack. This ensures we never exceed the limit on any single container. For the pop operation, I remove the top element from the last stack in the list. A critical detail here is handling the state after removal: if that stack becomes empty, I must remove it from the main list entirely to prevent returning invalid data or wasting memory. In a Stripe context, where transaction integrity is paramount, I would also ensure the pop method throws a clear exception if the entire structure is empty, rather than returning undefined values. Regarding performance, both operations run in constant time, O(1), because we only access the end of the list. The space complexity is linear relative to the number of items stored. I would verify this by tracing a scenario where we push exactly N items, creating N/K stacks, and then pop them all, confirming the list shrinks correctly as stacks empty.