PRIORITY QUEUE Collection of elements such that − Each element has been assigned a priority − The order in which elements are deleted and processed comes from the following rule n elememt of higher priority is processed before any element of lower priority Tw o elements with same priority are processed according to the order in which they were added to the !ueue Can be implemented using − One"way list − #ultiple !ueues
PRIORITY QUEUECollection of elements such thatEach element has
been assigned a priorityThe order in which elements are deleted and
processed comes from the following ruleAn elememt of higher
priority is processed before any element of lower priorityTwo
elements with same priority are processed according to the order in
which they were added to the queueCan be implemented usingOne-way
listMultiple queues
Array representation of priority queue
By using two dimensional array, we can represent priority
queue.
Example: PQ[2][20] , first rows is used to stores the queue
elements, Second row is used to store the priority of the
elements
Two pointers FRONT and REAR are used to represent two ends of
the queue.
ITEM1234567priority10877641
OperationsInsertions to the rearDeletions from front
Priority Queue insertionInput: ITEM and PRIORITY to be inserted
into PQOutput: ITEM inserted at REAR end of PQData structure: 2D
array PQ with FRONT and REAR pointerSteps:If (REAR=N)print queue is
full and exitelse if FRONT=0
FRONT=1endifREAR=REAR+1PQ[0][REAR]=ITEMPQ[1][REAR]=PRIORITYsort_PQ(PQ[])endifStop
Priority Queue DeletionInput: priority queue with two pointer
fromt and rearOutput: One item is deleted from the front end of the
priority queueData Structure: Priority queue is implemented by
using ArraySteps: If(front=-1) AND(rear=-1) Printf(Priority Queue
is empty) and Exit Else Item=PQ[0][front] Priority=PQ[1][front]
If(front=rear) Front=Rear=-1 Else Front=front+1 EndIf EndIf
Stop
