| 3 | |
| 4 | |
| 5 | class LinkedStack: |
| 6 | |
| 7 | class _Node: |
| 8 | __slots__ = "_element" , "_next" |
| 9 | |
| 10 | def __init__(self, element, next): |
| 11 | self._element = element |
| 12 | self._next = next |
| 13 | |
| 14 | def __init__(self): |
| 15 | self._head = None |
| 16 | self._size = 0 |
| 17 | |
| 18 | def __len__(self): |
| 19 | return self._size |
| 20 | |
| 21 | |
| 22 | def is_empty(self): |
| 23 | return self._size == 0 |
| 24 | |
| 25 | def push(self, e): |
| 26 | self._head = self._Node(e, self._head) |
| 27 | self._size += 1 |
| 28 | |
| 29 | def top(self): |
| 30 | if self.is_empty(): |
| 31 | raise Empty("stack is empty") |
| 32 | return self._head._element |
| 33 | |
| 34 | |
| 35 | def pop(self): |
| 36 | if self.is_empty(): |
| 37 | raise Empty("stack is emoty") |
| 38 | |
| 39 | answer = self._head._element |
| 40 | self._head = self._head._next |
| 41 | self._size -= 1 |
| 42 | return answer |
| 43 | |