How do I implement a stack in programming?

How do I implement a stack in programming?

To implement a stack, you can use an array or a linked list. Which programming language are you using?

I'm using Python. Can you show me an example?

Sure! Here's a simple stack implementation using a list in Python:

class Stack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        return self.items.pop() if not self.is_empty() else None

    def is_empty(self):
        return len(self.items) == 0

    def peek(self):
        return self.items[-1] if not self.is_empty() else None

    def size(self):
        return len(self.items)

What if I want to implement it using a linked list?

Here's how you can implement a stack using a linked list in Python:

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

class Stack:
    def __init__(self):
        self.top = None

    def push(self, data):
        new_node = Node(data)
        new_node.next = self.top
        self.top = new_node

    def pop(self):
        if self.is_empty():
            return None
        popped_node = self.top
        self.top = self.top.next
        return popped_node.data

    def is_empty(self):
        return self.top is None

    def peek(self):
        return self.top.data if not self.is_empty() else None