Tutorials

Queue


Queue Insertion


We can insert element in the queue from rear end as shown below:

insert item in queue by tutorialsinhand.com

 

From the above diagram we see:

  • When queue is empty, both front and rear are assigned as -1. 
  • During insertion of element the value of rear is incremented by 1. (R=R+1)
  • On insertion of the first element (7), both the front and rear is incremented by 1 (F=R=0). Front will get incremented only once when first element is added. After this front is never increased for insertion operation.
  • During insertion of second element, front remains at 0 while rear is incremented by 1 (R=1)
  • During insertion of third element, front remains at 0 while rear is incremented by 1 (R=2)
  • It will go on for all addition operation. Front will not increase from 0 while rear will keep incrementing by 1.

Algorithm

Given below is the algorithm to insert item at the rear end of the queue.

  1. Initialize Front = -1, Rear = -1 
  2. Repeat step 3 to 7 if  Rear < MaxSize - 1 is true
  3. Read item
  4. if Front == -1 then Front = 0 and Rear =0 
  5. Else Rear = Rear + 1
  6. End if
  7. Set Queue[Rear] = item
  8. Print "Queue overflow"

 



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