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Interactive program to simulate Queue functionality using Linked list


/*
 * Copy right by Shiv Yaragatti
 * you are free to use, modify  and redistribute code on own risk
 * Interactive C Program to implement Queue using  linked list
 */

/* header needs have all required header files like stdio.h etc */
 #include "header.h"

struct queue {
int data;
struct queue *next;
};
typedef struct queue *Q;

/* Queue head */
struct qhead_struct {
struct queue  *head;
struct queue  *tail;
};
typedef struct qhead_struct  *H;

/* Insert elements into queue */
void insert(H *hq)
{
  int e;
  Q temp;
 temp= malloc(sizeof(struct queue));
 if(!temp) {
   printf("Can't allocate memory\n");
   return;
 }
 printf("Enter element\n");
 scanf("%d", &e);
 temp->data =e;
 temp->next = NULL;

/* add element queue at tail */
 if((*hq)->head == NULL) {
    (*hq)->head =(*hq)->tail =temp;
 } else {
    (*hq)->tail->next = temp;
    (*hq)->tail = temp;
    
 }
   
}

/* delete elements from queue */
void del(H *hq){
Q temp;
 temp= (*hq)->head;
 if((*hq)->;head == NULL){
    printf("Q is empty ..\n");
    return;
 }
printf("Deleted element is %d\n", temp->data);
/* delete from head */ 
 (*hq)->head = (*hq)->head->next; 
 free(temp);

}

/* Display elements in the queue */
void display(H hq){
      Q temp;

 if(hq->head == NULL){
    printf("Empty Queue\n");
    return;
 }
 temp=hq->head;
 printf("Elements in Queue are \n");
 while(temp){
    printf("%d\n", temp->data);
    temp=temp->next;
 }
}

/* main program to help simulate queue operations */
int main()
{
 struct qhead_struct *qhead;
 int ch;
 
 qhead = malloc(sizeof(struct qhead_struct));
 qhead->head = NULL;
 qhead->tail = NULL;
 while(1) {
 system("clear");
 printf("1 Insert\n2 del\n3 display\n4 exit\n");
 printf("Enter you choice\n");
 scanf("%d", &ch);
 switch(ch) {
   case 1: insert(&qhead);
       break;
   case 2: del(&qhead); 
       break;
   case 3: display(qhead);
       break;
   case 4: exit(0);
   default: printf("Invalid choice\n");
 }
getchar();
getchar();
}
return 0;
}
   
/* end of the program */
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