Implement ascending priority queue - C Program

Write a C program to implement ascending priority queue with following functions  (use double pointers).
i) insert
ii) serve
iii) display

Solution:

Priority Queue:
It is an abstract data type which is like a regular queue, but in priority queue each element has a priority. The order of queue is First In First Out (FIFO).

In this example we insert and display the element of priority queue. The malloc function is used for dynamic array.

Program

#include<stdio.h>
#include<conio.h>
#include<malloc.h>
typedef struct que
{
    int info,prio;
    struct que *next;
}nodetype;
void insert(nodetype**,nodetype**,int,int);
void serve(nodetype**,nodetype**);
void display(nodetype*);
void main()
{
    nodetype *front=NULL,*rear=NULL;
    int ch,pr,num,c=0;
    printf("Menu\n1.Insert\n2.serve\n3.Display\n4.Exit\nChoice : ");
    do
    {
        scanf("%d",&ch);
        switch(ch)
        {
             case 1: printf("\nEnter the number to be inserted and its priority : ");
             scanf("%d  %d",&num,&pr);
             insert(&front,&rear,num,pr);
             break;
             case 2: if(front==NULL)
             printf("\nNo elements are present in the Priority Queue");
             else
             serve(&front,&rear);
             break;
             case 3: if(front==NULL)
             printf("\nNo elements in the Priority Queue");
             else
             display(front);
             break;
             default:
             printf("\nEnter the correct choice");
        }
        printf("press 1 to continue\n");
        scanf("%d",&c);
    }while(c==1);
}
void insert(nodetype **front,nodetype **rear,int num,int pr)
{
    nodetype *p=NULL,*tmp=*front;
    p=(nodetype*)malloc(sizeof(nodetype));
    if(p!=NULL)
    {
         p->info=num;
         p->prio=pr;
         p->next=NULL;
    }
    if((*rear)==NULL)
    {
         (*front)=(*rear)=p;
    }
    else
    {
         if((p->prio)>((*rear)->prio))
         {
              (*rear)->next=p;
              (*rear)=p;
         }
         else if(p->prio<((*front)->prio))
         {
              p->next=(*front);
              (*front)=p;
         }
         else
         {
              while(((tmp->next)->prio)<(p->prio))
              tmp=tmp->next;
              p->next=tmp->next;
              tmp->next=p;
         }
    }
}
void serve(nodetype **front,nodetype **rear)
{
    nodetype *tmp=*front;
    if((*front)==(*rear))
    {
        printf("The served element is %d",(*front)->info);
        (*rear)=(*front)=NULL;
    }
    else
    {
        printf("The served element is %d",(*front)->info);
        (*front)=(*front)->next;
    }
    free(tmp);
}
void display(nodetype *front)
{
    nodetype *tmp;
    tmp=front;
    while(tmp!=NULL)
    {
         printf("%d ",tmp->info);
         tmp=tmp->next;
    }
}


Output:

ascending priority queue
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