Stacks
Stacks Introduction
- A stack is a data structure that acts as a collection of elements and performs the two basic operations push (insertion) and pop (deletion). In this post, we'll examine various Python implementation and usage strategies for the stack..
- The top element is always removed first from a stack and is always added to it whenever a new element is added.
- Stacks contain an ordered set of data.
- Stack also provides a method named peek which returns the data at the top of the stack.
- This is a Last In, First Out or LIFO structure. A less frequently used term is First In, Last Out, or FILO.
- Stacks are used to implement searches in Graphs and Trees, which are other complex data structures.
- Examples include: Back and Forward in a browser, A pile of books, utensils in a dishwasher, In recursion, etc.
Stacks Implementation
These are the following Methods used in Stacks Implementation:
-
stack.isEmpty()
- The stack.isEmpty() method returns True if the stack is empty. Else, returns False
- stack.length()
- The stack.length() method returns the length of the stack.
- stack.top()
- The stack.top() method returns the top element in the stack.
- stack.push(x)
- The stack.push() method inserts the element, x to the top of the stack.
- stack.pop()
- The stack.pop() method removes the top element of the stack and returns it.
A list can be used to create stacks. And We can use append and pop method of lists.
class Stack:
def __init__(self):
self.stack = []
def isEmpty(self) -> bool:
return True if len(self.stack) == 0 else False
def length(self) -> int:
return len(self.stack)
def top(self) -> int:
return self.stack[-1]
def push(self, m: int) -> None:
self.m = m
self.stack.append(m)
def pop(self) -> None:
self.stack.pop()
