Question

i want to create queue with dynamic array, the problem is when i test the q.rear value in int main() (for inserting data later) it’s not -1 anymore. Which part did i do wrong?

here’s a piece of the code:

#include <stdio.h>
#include <conio2.h>
#include <stdlib.h>

typedef struct{
    int *data;
    int front,rear,max;
    }tqueue;
tqueue create(int size)
{
   tqueue q;
   q.data=(int *)malloc(size*sizeof(int));          
   q.front=0;
   q.rear=-1;
   q.max=size;
   return q;   
}
int main()
{
   tqueue q;
   int size=4;
   create(size);
   printf("\n%d",q.rear);
   getch();   
   return 0;
}

Answer 1

You didn’t assign the result of create() to q. The following calls create() and discards the result, leaving q in its original state:

create(size);

To fix, replace the above line with:

q = create(size);