Circular Queue

Queue

Queue is a linear data structure
FIFO (First in First Out)
Abstract Data Type
Insertion from Rear(R) and deletion from Front (F) operation
Enqueue - insertion of element
Dequeue - deletion of element



Algorithm for Enqueue and Dequeue operation in circular queue
r : rear
f: front
N: size of queue
index starts with 0 (zero)








Function to check queue state

Algorithm isEmpty()
{
      if( f= = -1 && r = = -1)
                      return true
        else
                      return false

}



Algorithm to insert an element in queue

Algorithm Enqueue()
{
      if ( (r+1)% N) = f)
              returen overflow

      elseif ( isEmpty())
               f = r = 0
               else
                        r= (r+1)% N

        A[r] = x
}




Algorithm Dequeue()
{
       if( (isEmpty() )
       {
               return underflow

          elseif (f= r)
                    f = r = -1
                else
                      f= (f+1) % N

}
   


For a given Queue of size N (=5) do following operation:

Enqueue 4,  Enqueue 7, Enqueue 9, Dequeue (),  Enqueue 2,  enqueue 5 , Enqueue 8, Enqueue 6, Dequeue(), Dequeue ()

trace your program using above algorithm.





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