C Program to implement Circular Queue.

Problems:  Write a C program to implement a circular queue that contains a list of names.  

Data Structure Definition:

Node: A node is a basic building block of a linked list. A node may contain different segments, but basically it contains two parts which are as followed,

 

                                    Data or information part : It stores the data in the node

                                       Link part : It points to the next node or holds the address to the next node.

Source Code:

#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#define MAX 10

//defining the basic element of the queue
typedef struct Q
{
	int R,F;
	char *data[MAX];
}Q;

//declaration of functions
void initialise(Q *P);
int empty(Q *P);
int full(Q *P);
void enqueue(Q *P,char *x);
char * dequeue(Q *P);
void print(Q *P);

//main function
int main()
{	
	//intializing a node named queue
	Q q;
	
	//declaration and initialization fof variables
    int op;
    char x[40],*y;
    
    //initializ the queue
    initialise(&q);
        
	do{
			//displaying the menu
			printf("\n\n 1) Enqueue\n 2) Dequeue\n 3) Print\n 4) Quit");
			
			//inputting the input choice 
			printf("\n Enter Your Choice : ");
			scanf("%d",&op);
		
			//calling functions and passing arguments through the functions as per th choice of the user
			switch(op)
	 		{ 
			 	case 1: 
				 	printf("\n Enter string : ");
				    fflush(stdin);
		    		scanf("%s",x);
		    		if(!full(&q))
					{
						y=(char*)malloc(strlen(x)+1);
						strcpy(y,x);
						enqueue(&q,y);
					}
		    		else
						printf("\n Queue is full !!!!");
		        				break;
	   			case 2:	
				    if(!empty(&q))
		    		{
						y=dequeue(&q);
						printf("\n Deleted Data = %s",y);
		    		}
		   			else
						printf("\n Queue is empty !!!!");
		   				break;
	   			case 3: 
				   		print(&q);a
						break;
	}
      }while(op!=4);
}

//function to initialize a circular queue
void initialise(Q *P)
{
	//declaration of variable
	int i;
	//initializing the queue
	for(i=0;i<MAX;i++)
		P->data[i]=NULL;
	P->R=-1;
	P->F=-1;
}

//function to check if the queue is empty
int empty(Q *P)
{
	//if the queue is empty, return 1 else, return 0
	if(P->R==-1)
		return(1);
	return(0);
}

//function to check if the queue is full
int full(Q *P)
{
	//return 1 if the queue is full, else return 0
	if((P->R+1)%MAX==P->F)
		return(1);
	return(0);
}

//function to enqueue and element in the queue
void enqueue(Q *P,char *x)
{
	//enqueueing the element
	if(P->R==-1)
	{
		P->R=P->F=0;
		if(P->data[P->R]!=NULL)
			free(P->data[P->R]);
		P->data[P->R]=x;
	}
	else
	{
		P->R=(P->R+1)%MAX;
		if(P->data[P->R]!=NULL)
			free(P->data[P->R]);
		P->data[P->R]=x;
	}
}

//function to dequeue 
char * dequeue(Q *P)
{
	//declaring a character type pointer
	char *x;
	
	//dequeing the element from the queue
	x=P->data[P->F];
	if(P->R==P->F)
	{
		P->R=-1;
		P->F=-1;
	}
	else
		P->F=(P->F+1)%MAX;
	return(x);
}

//function to display the elements of the queue
void print(Q *P)
{
	int i;
	if(!empty(P))
	{
		printf("\n");
		for(i=P->F;i!=P->R;i=(i+1)%MAX)
			printf("%s\t",P->data[i]);
	}
       printf("%s\t",P->data[i]);
}

Output:

 1) Enqueue

 2) Dequeue

 3) Print

 4) Quit

 Enter Your Choice : 1

 

 Enter string : computer

 

 1) Enqueue

 2) Dequeue

 3) Print

 4) Quit

 Enter Your Choice : 1

 

 Enter string : science

 

1) Enqueue

 2) Dequeue

 3) Print

 4) Quit

 Enter Your Choice : 1

 

Enter string : honours

 

 1) Enqueue

 2) Dequeue

 3) Print

 4) Quit

 Enter Your Choice : 3

 

computer        science   honours

 

1) Enqueue

 2) Dequeue

 3) Print

 4) Quit

 Enter Your Choice : 2

 

 Deleted Data = computer

 

 1) Enqueue

 2) Dequeue

 3) Print

 4) Quit

 Enter Your Choice : 2

 

 Deleted Data = science

 

 1) Enqueue

 2) Dequeue

 3) Print

 4) Quit

 Enter Your Choice : 2

 

 Deleted Data = honours

 

 1) Enqueue

 2) Dequeue

 3) Print

 4) Quit

Enter Your Choice : 2

 

 Queue is empty !!!!