Pushing a Queue onto a Stack?

The basic idea of this program is to keep track of different trains that come into a train station, and store each train's car number in a queue. The last train to enter must be the first train to leave, so I know I need to somehow store the queue holding the trains' information in a stack. However, I keep getting a strange output when I tried to push the queue directly onto the stack. I'm not sure if I am having an issue where I first created the stack, or I am just not using the push command properly.

Here is the code where I initialized the queue and stack:

Code:

---

struct station* new_station(int Initial_Size) //my stack
{
    struct station* s;
   
    s = malloc(sizeof(struct station));
   
    s->store = calloc(Initial_Size, sizeof(int));
    s->top = 0;
    s->size = Initial_Size;
   
    return s;
}

struct train* new_train(int initial_size) //my queue
{
    struct train* q;
   
    q = malloc(sizeof(struct train));
    q->store = calloc(initial_size, sizeof(int));
    q->front = 0;
    q->back = 0;
    q->size = initial_size;
   
    return q; 
}

---

And here is the function I came up with to store the information:

Code:

---

void add_train(struct station* s, struct train* q, int num_cars, FILE* finfo)
{
    int i;
    int j;
    int car;

    for(i = 0; i < num_cars; i++)
    {
        fscanf(finfo, "&#37;d", &car);
        q->store[q->back] = car;
        q->back = (q->back + 1) % q->size;
        //expand queue check
    }

    s->store[s->top] = q->store;
    s->top++;
    for(j = 0; j < s->top; j++)
    {
        printf("%d\n", s->store[j]);
    }
    return; 
}

---

I'm not sure what I can do to fix this problem. Anyone have any ideas?

So your train is a queue of ints, representing the car numbers. That means your station needs to be a stack of trains (not ints), or at least pointers to trains, and then you would do s->store[s->top] = q.

Why store the train's car number in a queue and on a stack i.e. two different places when they can all be made to fit on a stack for easy storage and retrieval. The queue and stack are complementary data structures. The queue is a FIFO while a stack is a LIFO. As the last train must be the first one to leave you need to use a LIFO type data structure which is a stack. So forget about using a queue and focus on pushing and popping items items on the stack. Can you list the members of the struct train and struct station types.

^^ I figured I would need to make it so that I have a stack of queues, but I'm not sure how to put that into code. It would have to be something in the function when I create the stack, right? I'm not sure how to go about fixing that part.

^ I don't think I see what you are saying with being able to not use a queue, but I can post the two structs.

Code:

---

struct station
{
    int* store;
    int top;
    int size;
};

struct train
{
    int* store;
    int front;
    int back;
    int size;
};

---

Quote:

---

Originally Posted by MiroMage

Code:

---

struct station
{
    struct train * store;
    int top;
    int size;
};

struct train
{
    int* store;
    int front;
    int back;
    int size;
};

---

---

Your station needs to store trains, not ints. (And of course you would need to define struct train first.)

Ah, alright. Thanks a lot! And the way it is stored on the stack will only store it once, right? Because when I put in a print function, it printed the second queue twice, the third queue three times, and so on. That might be a problem with my print function, but I just wanted to make sure that I am not really stacking the same queue multiple times.