Stack

What is stack?

Stack is a Last In First Out (LIFO) manner and it is built by dynamic array. That means the last element added will be the 1st element to come out first.

stack

Operation	Big-O Time
Push	O(1)
Pop	O(1)
Peek / Top	O(1)

class Stack:
    def __init__(self) -> None:
        self.stack = []
 
    def __len__(self) -> int:
        return len(self.stack)
 
    def push(self, n) -> None:
        self.stack.append(n)
 
    def pop(self):
        if len(self) == 0:
            raise Exception("Stack is empty")
        return self.stack.pop()
 
    def peek(self):
        if len(self) == 0:
            raise Exception("Stack is empty")
        return self.stack[-1]

What is stack?

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