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Stacks.py
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Stacks.py
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"""
Author: Ahmad Elkholi
Created on Wed Oct 20 13:54:12 2022
Stack data structure implementations using lists and linked lists.
"""
from typing import Any
from LinkedLists import SinglyLL
FULL_STACK_ERROR_MSG = "Maximum stack capacity reached, unable to store more elements."
EMPTY_STACK_ERROR_MSG = "Stack is empty."
class Stack:
"""List-based implementation of the Stack data structure.
Parameters
----------
capacity: int
Determine the maximum amount of elements a Stack can carry. If unspecified, Stack capacity will be limitless.
default = None
vals: iterable
a group of elements that are added to the Stack during its construction. If unspecified, an empty Stack is created. If the number of elements in vals exceeds the specified capacity, An assertion error is raised.
default = None
Methods
-------
empty() -> bool:
Check if the stack is empty.
full() -> bool:
Check if the stack is full.
push(element) -> self:
Add an element to the top of the stack.
pop() -> Any:
Remove the top element in the stack.
peek() -> Any:
Access the top element of the stack.
delete() -> None:
Remove all elements from the stack.
"""
def __init__(self, capacity: int = None, vals: list = None) -> None:
self._assert_params(capacity, vals)
self._capacity = capacity
self._elements = list(vals) if vals else []
self._size = len(self._elements)
def __repr__(self) -> str:
return f"Stack({self._elements})"
def __len__(self) -> int:
return self._size
def __iter__(self):
return iter(self._elements)
def __contains__(self, element) -> bool:
return element in self._elements
def _assert_params(self, capacity, vals) -> None:
if capacity is not None:
if not isinstance(capacity, int):
raise TypeError("capacity must be of type 'int'.")
if capacity <= 0:
raise ValueError("capacity must be greater than zero.")
if vals is not None:
if not hasattr(vals, "__iter__"):
raise TypeError("vals is not iterable")
if capacity is not None:
assert (
len(vals) <= capacity
), f"Cannot create stack with {len(vals)} elements and max capacity of {capacity}."
def empty(self) -> bool:
"""Check if the stack is empty."""
return self._size == 0
def full(self) -> bool:
"""Check if the stack is full."""
return self._size == self._capacity
def push(self, element: Any):
"""Add an element to the top of the stack.
Parameters
----------
element: Any
The element that is added to the stack.
Returns
-------
self
"""
assert not self.full(), FULL_STACK_ERROR_MSG
self._elements.append(element)
self._size += 1
return self
def pop(self) -> Any:
"""Remove the top element in the stack.
Returns
-------
Element: Any
The top element in the stack.
"""
assert not self.empty(), EMPTY_STACK_ERROR_MSG
self._size -= 1
return self._elements.pop()
def peek(self) -> Any:
"""Access the top element of the stack.
Returns
-------
Element: Any
The top element in the stack.
"""
assert not self.empty(), EMPTY_STACK_ERROR_MSG
return self._elements[-1]
def delete(self) -> None:
"""Remove all elements from the stack."""
self._elements = []
self._size = 0
class StackLL(Stack):
"""LinkedList-based implementation of the Stack data structure.
Parameters
----------
capacity: int
Determine the maximum amount of elements a Stack can carry. If unspecified, Stack capacity will be limitless.
default = None
vals: iterable
a group of elements that are added to the Stack during its construction. If unspecified, an empty Stack is created. If the number of elements in `vals` exceeds the specified capacity, An assertion error is raised.
default = None
Methods
-------
empty() -> bool:
Check if the stack is empty.
full() -> bool:
Check if the stack is full.
push(element) -> self:
Add an element to the top of the stack.
pop() -> Any:
Remove the top element in the stack.
peek() -> Any:
Access the top element of the stack.
delete() -> None:
Remove all elements from the stack.
"""
def __init__(self, capacity: int = None, vals: list = None) -> None:
self._assert_params(capacity, vals)
self._capacity = capacity
self._elements = SinglyLL(vals)
self._size = len(self._elements)
def push(self, element: Any):
"""Add an element to the top of the stack.
Parameters
----------
element: Any
The element that is added to the stack.
Returns
-------
self
"""
assert not self.full(), FULL_STACK_ERROR_MSG
self._elements.insert(element)
self._size += 1
return self
def pop(self) -> Any:
"""Remove the top element in the stack.
Returns
-------
Element: Any
The first element in the stack.
"""
assert not self.empty(), EMPTY_STACK_ERROR_MSG
removed_element = self.peek()
self._elements.pop()
self._size -= 1
return removed_element
def peek(self) -> Any:
"""Access the top element of the stack.
Returns
-------
Element: Any
The top element in the stack.
"""
assert not self.empty(), EMPTY_STACK_ERROR_MSG
return self._elements.tail.data
def delete(self) -> None:
"""Remove all elements from the stack."""
self._elements.delete()
self._size = 0