P queue

#include <stdio.h>

#include <stdlib.h>

#define MAX 5
void insert_by_priority(int);
void delete_by_priority(int);
void create();
void check(int);
void display_pqueue();
int pri_que[MAX];
int front, rear;
void main()
{
 int n, ch;
 printf("\n1 - Insert an element into queue");
 printf("\n2 - Delete an element from queue");
 printf("\n3 - Display queue elements");
 printf("\n4 - Exit");
 create();
 while (1)
 {
 printf("\nEnter your choice : "); 
 scanf("%d", &ch);
 switch (ch)
 {
 case 1: 
 printf("\nEnter value to be inserted : ");
 scanf("%d",&n);
 insert_by_priority(n);
 break;
 case 2:
 printf("\nEnter value to delete : ");
 scanf("%d",&n);
 delete_by_priority(n);

 break;

 case 3: 
 display_pqueue();
 break;
 case 4: 
 exit(0);
 default: 
 printf("\nChoice is incorrect, Enter a correct choice");
 }
 }
}
/* Function to create an empty priority queue */
void create()
{
 front = rear = -1;
}
/* Function to insert value into priority queue */
void insert_by_priority(int data)
{
 if (rear >= MAX - 1)
 {
 printf("\nQueue overflow no more elements can be inserted");
 return;
 }
 if ((front == -1) && (rear == -1))
 {
 front++;
 rear++;
 pri_que[rear] = data;
 return;
 } 
 else
 check(data);
 rear++;
}
/* Function to check priority and place element */
void check(int data)
{
 int i,j;
for (i = 0; i <= rear; i++)

 {

 if (data >= pri_que[i])
 {
 for (j = rear + 1; j > i; j--)
 {
 pri_que[j] = pri_que[j - 1];
 }
 pri_que[i] = data;
 return;
 }
 }
 pri_que[i] = data;
}
/* Function to delete an element from queue */
void delete_by_priority(int data)
{
 int i;
 if ((front==-1) && (rear==-1))
 {
 printf("\nQueue is empty no elements to delete");
 return;
 }
 for (i = 0; i <= rear; i++)
 {
 if (data == pri_que[i])
 {
 for (; i < rear; i++)
 {
 pri_que[i] = pri_que[i + 1];
 }
 pri_que[i] = -99;
 rear--;
 if (rear == -1) 
 front = -1;
 return;
 }
 }
 printf("\n%d not found in queue to delete", data);
}

/* Function to display queue elements */

void display_pqueue()
{
 if ((front == -1) && (rear == -1))
 {
 printf("\nQueue is empty");
 return;
 }
 for (; front <= rear; front++)
 {
 printf(" %d ", pri_que[front]);
 }
 front = 0;
}