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queue.py
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queue.py
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class Node:
"""
A single node of a linked list
"""
def __init__(self, val: int):
self.val: int = val
self.next: Node | None = None
class Queue:
"""
Queue: FIFO (First in First out)
"""
def __init__(self):
self.queue: Node | None = None
self.tail: Node | None = None
self.length = 0
def __len__(self) -> int:
"""
Get queue length
time complexity: O(1)
"""
return self.length
def is_empty(self) -> bool:
"""
Check if the queue is empty
time complexity: O(1)
"""
return self.length == 0
def enqueue(self, val: int) -> None:
"""
Add a new item to the queue
time complexity: O(1)
"""
node = Node(val)
self.length += 1
if self.queue is None:
self.queue = node
self.tail = self.queue
else:
self.tail.next = node
self.tail = self.tail.next
def dequeue(self) -> int:
"""
Dequeue an item from queue
time complexity: O(1)
"""
if self.queue is not None:
val = self.queue.val
self.queue = self.queue.next
self.length -= 1
return val
if self.queue is None:
self.tail = None
return -1
def peek(self) -> int:
"""
Get last item from stack without popping
time complexity: O(1)
"""
if self.queue is not None:
return self.queue.val
return -1
def __str__(self) -> str:
"""
Show queue data
time complexity: O(n)
"""
current = self.queue
string = ""
while current is not None:
string += f"{current.val}\n"
current = current.next
return string