Question

Consider you have an array of some random size. You need to perform dequeue operation. You can perform it using stack operation (push and pop) or using queue operations itself (enQueue and Dequeue). The output is guaranteed to be same. Find some differences?

(a) They will have different time complexities

(b) The memory used will not be different

(c) There are chances that output might be different

(d) No differences

Answer 1

The correct choice is (a) They will have different time complexities

The explanation is: To perform operations such as Dequeue using stack operation you need to empty all the elements from the current stack and push it into the next stack, resulting in a O(number of elements) complexity whereas the time complexity of dequeue operation itself is O(1). And there is a need of a extra stack. Therefore more memory is needed.