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If the size of S1 and S2 is 0, return -1.3+ years of programming experience with Java and C++. The array - Answered by a verified Programmer. Space Complexity: O(N) Approach 2: Making dequeue operation costly How do you write a pseudocode with the functions of enqueue and dequeue This above will have a fixed array. Time Complexity: O(N) for enqueue operation, O(1) for pop dequeue () :- It removes and returns the maximum/minimum element of the queue. The Queue data structure will supports the following operations: enqueue (N) :- It insert element N to the back of the queue.

Else, return the top element of the stack.Push all the elements from S2 back to S1.Push the element that needs to be inserted into S1.Else, push all the elements from S1 to S2.If S1 is empty, insert the element into S2.Therefore, we will use a second stack for the same. Therefore, we need to devise a technique using stacks, such that the element which will be pushed will remain at the top. Approach 1: Making enqueue operation costlyĪs discussed above, we know, in the queue, it follows a FIFO order, i.e., the element which gets in first, gets out first. So, if you clearly observe, we would require two stacks to implement the queue, one for en queue and another for de queue operation.

It supports enqueue, dequeue, peek operations. Push and pop operations take place through two ends of the queue. Queue is First In First Out data structure. Push and pop operations take place only through one end of the stack i.e. Stack is Last in First Out data structure.

MyQueue.push(2) // queue is: (leftmost is front of the queue)īefore diving into the solution, let us first understand the basic difference between Stack and Queue. The queue should support all functions such as push, pop, peek. The task here is to implement a First In First Out queue using Stacks. Approach 2: Making dequeue operation costly.Approach 1: Making enqueue operation costly.