Stack Using a Queue

Problem

Simulate a stack using only a single queue.

operations contains "push", "pop", "top", or "empty"; values provides the pushed value (ignored otherwise). On push, append the value and then rotate all earlier elements behind it so the newest element is always at the front. Record None for push, the removed value (or None if empty) for pop, the top value (or None if empty) for top, and a boolean for empty.

Return the list of recorded results.

Hint

After appending, rotate the new element to the front by moving n-1 elements to the back.

Test cases

case 1

in: [["push","push","top","pop","empty"],[1,2,0,0,0]]

expected: [null,null,2,2,false]

case 2

in: [["pop","top","empty"],[0,0,0]]

expected: [null,null,true]

case 3

in: [["push","pop","pop"],[5,0,0]]

expected: [null,5,null]

case 4

in: [["push","push","push","pop"],[1,2,3,0]]

expected: [null,null,null,3]

Starter codePython

def queue_stack_ops(operations, values):
    # Your code here
    pass

4 test cases · run your code against them in the editor