Stack Data Structure

Hello, in this article we're going to talk about stack;

Definition of Stack

"A stack is a linear data structure that stores items in a Last-In/First-Out (LIFO) or First-In/Last-Out (FILO) manner. In stack, a new element is added at one end and an element is removed from that end only. The insert and delete operations are often called push and pop."

• www.geeksforgeeks.org

Space and Time complexity

the space complexity of a stack is O(n)

push	pop	peek
O(1)	O(1)	O(1)

implementation of a stack using list in python

class Stack :
    def __init__(self):
        self.items = []
        self.top = 0

    def push(self,data: any) -> any :
        self.items.append(data)
        self.top+=1
        return data

    def pop(self) -> any:
        if self.top > 0 :
            self.top -=1
            return self.items.pop()
    def peek(self) -> any:
        if self.top > 0:
            return self.items[-1]

    def __len__(self) -> int:
        return self.top

    def clear(self) -> list:
        self.items = []
        self.top = 0
        return self.items

    def isEmpty(self) -> bool:
        return self.items == []

    def printAll(self) -> list:
        return self.items

References and useful Ressources

• https://www.quora.com/What-are-the-advantages-and-disadvantages-of-stack-in-collection
• https://www.geeksforgeeks.org/stack-in-python/
• https://betterprogramming.pub/implementing-a-stack-in-javascript-73d1aa0483c1

thank you!
#day_2