Bubble sort - linked list

#define MAX 10

struct lnode
{
int data;
struct lnode *next;
} *head, *visit;

/* add a new entry to the linked list */
void llist_add(struct lnode **q, int num);
/* preform a bubble sort on the linked list */
void llist_bubble_sort(void);
/* print the entire linked list */
void llist_print(void);

int main(void) {
/* linked list */
struct lnode *newnode = NULL;
int i = 0; /* a general counter */

/* load some random values into the linked list */
for(i = 0; i < MAX; i++)
{
llist_add(&newnode, (rand() % 100));
}

head = newnode;
printf("Before bubble sort:\n");
llist_print();
printf("After bubble sort:\n");
llist_bubble_sort();
llist_print();

return 0;
}

/* adds a node at the end of a linked list */
void llist_add(struct lnode **q, int num)
{
struct lnode *tmp;

tmp = *q;

/* if the list is empty, create first node */
if(*q == NULL) {
*q = malloc(sizeof(struct lnode));
tmp = *q;
} else {
/* go to last node */
while(tmp->next != NULL)
tmp = tmp->next;

/* add node at the end */
tmp->next = malloc(sizeof(struct lnode));
tmp = tmp->next;
}

/* assign data to the last node */
tmp->data = num;
tmp->next = NULL;
}

/* print the entire linked list */
void llist_print(void)
{
visit = head;

while(visit != NULL)
{
printf("%d ", visit->data);
visit = visit->next;
}
printf("\n");
}

/* preform a bubble sort on the linked list */
void llist_bubble_sort(void) {
struct lnode *a = NULL;
struct lnode *b = NULL;
struct lnode *c = NULL;
struct lnode *e = NULL;
struct lnode *tmp = NULL;

/*
// the `c' node precedes the `a' and `e' node
// pointing up the node to which the comparisons
// are being made.
*/
while(e != head->next)
{
c = a = head;
b = a->next;
while(a != e)
{
if(a->data > b->data)
{
if(a == head)
{
tmp = b -> next;
b->next = a;
a->next = tmp;
head = b;
c = b;
} else {
tmp = b->next;
b->next = a;
a->next = tmp;
c->next = b;
c = b;
}
} else
{
c = a;
a = a->next;
}
b = a->next;
if(b == e)
e = a;
}
}
}

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