QUEUE By Rajanikanth B www btechsmartclass com Introduction

QUEUE By Rajanikanth B www. btechsmartclass. com

Introduction Queue is a linear Data Structure in which the operations are performed based on FIFO (First In First Out) principle. In a Queue always the Insertion operation is done at “rear” and Deletion operation is done at “front”. In a Queue sequence of elements entered into the queue is same as the sequence of elements leave the queue.

Queue Definition Fields • Queue is a linear Data Structure in which the operations are performed based on FIFO (First In First Out) principle. • rear – used to store the position of insertion • front – used to store the position of deletion • size – used to store the size of the queue • element – used to store the value to be inserted • en. Queue(element) – to insert into queue • de. Queue( ) – to delete from queue Functions • display( ) – to display all elements in queue Condition • Rear >= size – Queue is full • Front == rear – Queue is empty

Implementation #define size 10 void main() { int Q[size], front = -1, rear = -1, op, element; void en. Queue(int); void de. Queue(); void display(); printf(“Select your option: ”); printf(“ 1: Insertn 2: Deleten 3: Displayn”); scanf(“%d”, &op); switch(op) { case 1: printf(“Enter element to be insert: ”); scanf(“%d”, &element); en. Queue(element); break; case 2: de. Queue(); break; case 3: display(); break; } }

When the compiler executes above code it allocates memory as follows…. 0 1 2 3 4 5 . . . SIZE-1 Q f = r = -1 f = front r = rear Queue is EMPTY

Insertion en. Queue( int element ) { if( rear != size-1) { rear ++; Q[rear] = element; } else printf(“Queue is full !!!”); Queue is full !!! } 0 Q 1 2 3 10 20 30 40 4 5 6 7 8 9

Deletion de. Queue( ) { if( front != rear ) { front ++; printf(“n. Element removed : %d”, Q[front]); } else printf(“Queue is empty !!!)”; Queue is empty !!! } 0 Q 1 2 3 10 20 30 40 4 5 6 7 8 9

Display display( ) { if( front != rear ) { for(int i=front+1; i<=rear, i++) printf(“%dt”, Q[i]); } else printf(“Queue is empty !!!”); } 0 Q 1 2 3 10 20 30 40 4 5 6 7 8 9