A queue using two stacks (head and tail), the head stack keeps the elements in a queue order, it means ready to dequeue or print the top element. When necessary the last elements in the tail stack are moved to the head stack. The normalize_head method verify if its necessary
| 1 | class Queue: |
| 2 | """ |
| 3 | A queue using two stacks (head and tail), the head |
| 4 | stack keeps the elements in a queue order, it means |
| 5 | ready to dequeue or print the top element. |
| 6 | When necessary the last elements in the tail stack |
| 7 | are moved to the head stack. The normalize_head method |
| 8 | verify if its necessary to move elements from tail to head. |
| 9 | """ |
| 10 | head = [] |
| 11 | tail = [] |
| 12 | |
| 13 | def normalize_head(self): |
| 14 | if not self.head: |
| 15 | while self.tail: |
| 16 | self.head.append(self.tail.pop()) |
| 17 | |
| 18 | def enqueue(self, element): |
| 19 | self.tail.append(element) |
| 20 | |
| 21 | def dequeue(self): |
| 22 | self.normalize_head() |
| 23 | self.head.pop() |
| 24 | |
| 25 | def print_top(self): |
| 26 | self.normalize_head() |
| 27 | print(self.head[-1]) |
| 28 | |
| 29 | if __name__ == '__main__': |
| 30 | queue = Queue() |