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QueueUsingLinkedList.py
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114 lines (88 loc) · 3.11 KB
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# Python program to implement the queue data structure using linked lists.
# Node class represents each element in the queue
class Node:
def __init__(self, data: int):
self.data = data # Store the value of the node
self.next = None # Pointer to the next node
# Queue class implements queue operations using a linked list
class Queue:
def __init__(self):
# Pointers to the front and rear of the queue
self.front: Node | None = None
self.rear: Node | None = None
# Function to check if the queue is empty
def is_empty(self) -> bool:
# If front is None, the queue is empty
return self.front is None
# Function to add an element to the queue
def enqueue(self, data: int) -> None:
# Create a new node
new_node = Node(data)
# If the queue is empty, the new node is both front and rear
if self.rear is None:
self.front = self.rear = new_node
return
# Add the new node at the end and update rear
self.rear.next = new_node
self.rear = new_node
# Function to remove an element from the queue
def dequeue(self) -> int | None:
# If the queue is empty, return None
if self.is_empty():
print("Queue Underflow")
return None
# Get the data from front node
removed_data = self.front.data
# Move front pointer to the next node
self.front = self.front.next
# If front becomes None, then the queue is empty, so rear also becomes None
if self.front is None:
self.rear = None
# Return the removed data
return removed_data
# Function to get the front element of the queue
def get_front(self) -> int | None:
if self.is_empty():
print("Queue is empty")
return None
return self.front.data
# Function to get the rear element of the queue
def get_rear(self) -> int | None:
if self.is_empty():
print("Queue is empty")
return None
return self.rear.data
# Function to display the queue elements
def __str__(self) -> str:
values = []
current = self.front
while current:
values.append(str(current.data))
current = current.next
return " <- ".join(values)
# Driver code
if __name__ == "__main__":
q = Queue()
# Enqueue elements into the queue
q.enqueue(10)
q.enqueue(20)
# Display the queue, front, and rear elements
print("Queue:", q)
print("Queue Front:", q.get_front())
print("Queue Rear:", q.get_rear())
# Dequeue elements from the queue
print("Dequeued:", q.dequeue())
print("Dequeued:", q.dequeue())
# Display the queue after dequeue operations
print("Queue:", q)
# Enqueue more elements
q.enqueue(30)
q.enqueue(40)
q.enqueue(50)
print("Queue:", q)
# Dequeue an element
print("Dequeued:", q.dequeue())
# Display the queue, front, and rear elements
print("Queue:", q)
print("Queue Front:", q.get_front())
print("Queue Rear:", q.get_rear())