C using while loop with linked list

I have come to a problem where I try to use while loop on linked list. I have two linked lists, namely temp and graph. I am using a while loop to do tasks while(temp != NULL). To move on in each of the loop, I am assigning temp = temp->link. However, this code does not compile. I realize that recursive function could be a solution, but the function is actually way more complicated that I don't think recursive would be such a good idea. By the way, graph is already a built linked list. Thanks in advance!

P.S. It is part of homework.

temp = graph->link;
while(temp!=NULL){
    if(stack->link == NULL){
        stack->link = (node_pointer)malloc(sizeof(graph));
        stack->link->weight = temp->weight;
        stack->link->vertex = temp->vertex;
    }
    temp = temp->link; //Here is the problem.
}

edit:

stack and graph are both arrays of linked list:

typedef struct node *node_pointer;

struct node{
    int vertex;
    int weight;
    int visited;
    struct node *link;
};
node_pointer graph[50];
node_pointer stack[50];
node_pointer temp;