How do you implement a Stack using two Queues?

Difficulty: 5/10

Queue & Stack Mechanics, Adapter Pattern, Amortized Complexity

Stack Using Two Queues

A Stack can be implemented using two Queues by maintaining the newest element at the front of one queue. One approach makes Push O(n) and Pop O(1): insert the new element into the empty queue, move all existing elements behind it, and then swap the queues.

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1
Push complexity: O(n).
2
Pop complexity: O(1).
3
Peek complexity: O(1).
4
Auxiliary space: O(n).
5
The alternative design can make Push O(1) and Pop O(n), depending on the desired workload.

Scenario Questions

0-2 years experience

Follow-up Questions