Remove even numbers from queue - c

Question

I got stuck when trying to remove even number from queue in C programming. Here is the code:
My data structure for Queue:
typedef struct _listnode
{
int data;
struct _listnode *next;
} ListNode; // You should not change the definition of ListNode
typedef struct _linkedlist
{
int size;
ListNode *first;
} LinkedList; // You should not change the definition of LinkedList
typedef struct _queue
{
LinkedList list;
} Queue;
And I am calling from my main:
case 3:
deleteEven(&q); // You need to code this function
printf("Result:\n");
printList(&q.list);
break;
What I am trying to do is first, I tried to check if the queue is empty. Then I will get the linked list head and modulus with 2, if getting 0 means it's even number and then I will dequeue it from the queue.
However, with these code, when I try to dequeue even numbers from queue, it just stopped working and not showing any error message.
Anybody know how to solve this? Thanks in advance.

Answer 1

In your function deleteEven's while loop you do this -
free(odd->list.first->data); //problem 1
odd->list.first->data= odd->list.first->next; //problem 2- assigning pointer type to int
Problem 1- But you haven't allocated memory to odd->list.first->data , it is an integer variable. And if you try to free such thing can cause error in your program (you should not free memory not allocated by malloc or similar functions)
You allocate memory to odd , so free pointer odd.
Even you should not free inside your while loop, as you allocate memory only one time .
Problem 2 - You assign pointer type to int. That's may also be one of reason for this error .
You should write loop like this -
while (!isEmptyQueue(odd)) {
enqueue(que, odd->list.first->data);
odd->list.first= odd->list.first->next; // increment pointer
}
free(odd);
3. While calling function dequeue -
dequeue(que->list.first->data);
int is passed but it expects Queue * .
Its type is int but you return NULL from it (return -1 or something to show failure).