queue python
# Python program to
# demonstrate queue implementation
# using list
# Initializing a queue
queue = []
# Adding elements to the queue
queue.append('a')
queue.append('b')
queue.append('c')
print("Initial queue")
print(queue)
# Removing elements from the queue
print("\nElements dequeued from queue")
print(queue.pop(0))
print(queue.pop(0))
print(queue.pop(0))
print("\nQueue after removing elements")
print(queue)
# Uncommenting print(queue.pop(0))
# will raise and IndexError
# as the queue is now empty
class Queue:
def __init__(self, capacity):
self.front = self.size = 0
self.rear = capacity - 1
self.Q = [None] * capacity
self.capacity = capacity
def isFull(self):
return self.size == self.capacity
def isEmpty(self):
return self.size == 0
def EnQueue(self, item):
if self.isFull():
print("Full")
return
self.rear = (self.rear + 1) % (self.capacity)
self.Q[self.rear] = item
self.size = self.size + 1
print("%s enqueue to queue" %str(item))
def DeQueue(self):
if self.isEmpty():
return "Empty"
print("%s dequeued from queue" %str(self.Q[self.front]))
self.front = (self.front + 1) % (self.capacity)
self.size = self.size - 1
def que_front(self):
if self.isEmpty():
print("The Queue is empty")
print("Front item is ", self.Q[self.front])
def que_rear(self):
if self.isEmpty():
print("Queue is Empty")
print("The rear item is ", self.Q[self.rear])
queue = Queue(30)
queue.EnQueue(10)
queue.EnQueue(20)
queue.EnQueue(30)
queue.EnQueue(40)
queue.EnQueue(50)
queue.que_front()
print()
queue.DeQueue()
queue.que_front()
queue.que_rear()
print()
queue.DeQueue()
queue.que_front()
queue.que_rear()
from queue import PriorityQueue
class PqElement(object):
def __init__(self, value: int):
self.val = value
#Custom Compare Function (less than or equsal)
def __lt__(self, other):
"""self < obj."""
return self.val > other.val
#Print each element function
def __repr__(self):
return f'PQE:{self.val}'
#Usage-
pq = PriorityQueue()
pq.put(PqElement(v)) #Add Item - O(Log(n))
topValue = pq.get() #Pop top item - O(1)
topValue = pq.queue[0].val #Get top value - O(1)