PriorityQueue.py

class PriorityQueueNode:	
    def __init__(self, value, pr):
        self.data = value
        self.priority = pr
        self.next = None
		
# Implementation of Priority Queue
class PriorityQueue:
	def __init__(self):
		self.front = None
		
	def isEmpty(self):
		return True if self.front == None else False
	
	def push(self, value, priority):
		if self.isEmpty() == True:
			self.front = PriorityQueueNode(value,priority)
			return 1
			
		else:
			if self.front.priority > priority:
				newNode = PriorityQueueNode(value,priority)
				newNode.next = self.front

				self.front = newNode
				return 1
				
			else:
				temp = self.front
				while temp.next:
					if priority <= temp.next.priority:
						break
		
					temp = temp.next
				newNode = PriorityQueueNode(value,priority)
				newNode.next = temp.next
				temp.next = newNode
				return 1

	def pop(self):
		if self.isEmpty() == True:
			return
		else:
			self.front = self.front.next
			return 1

	def peek(self):
		if self.isEmpty() == True:
			return
		else:
			return self.front.data

	def traverse(self):
		if self.isEmpty() == True:
			return "Queue is Empty!"
		else:
			temp = self.front
			while temp:
				print(temp.data, end = " ")
				temp = temp.next

# Driver code
if __name__ == "__main__":
	# 7 -> 4 -> 5 -> 6
	pq = PriorityQueue()
	pq.push(4, 1)
	pq.push(5, 2)
	pq.push(6, 3)
	pq.push(7, 0)
	pq.traverse()
	pq.pop()