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.
| 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]