Selection sort linked list

#include "stdio.h"
#include "stdlib.h"

#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 selection sort on the linked list */
void llist_selection_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 selection sort:\n");
llist_print();
printf("After selection sort:\n");
llist_selection_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 *temp;

temp = *q;

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

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

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

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

/* traverse the entire linked list */
while(visit != NULL)
{
printf("%d ", visit->data);
visit = visit->next;
}
printf("\n");
}

void llist_selection_sort(void)
{
struct lnode *a = NULL;
struct lnode *b = NULL;
struct lnode *c = NULL;
struct lnode *d = NULL;
struct lnode *tmp = NULL;

a = c = head;
while(a->next != NULL)
{
d = b = a->next;
while(b != NULL) {
if(a->data > b->data)
{
/* neighboring linked list node */
if(a->next == b)
{
if(a == head)
{
a->next = b->next;
b->next = a;
tmp = a;
a = b;
b = tmp;
head = a;
c = a;
d = b;
b = b->next;
} else {
a->next = b->next;
b->next = a;
c->next = b;
tmp = a;
a = b;
b = tmp;
d = b;
b = b->next;
}
} else
{
if(a == head)
{
tmp = b->next;
b->next = a->next;
a->next = tmp;
d->next = a;
tmp = a;
a = b;
b = tmp;
d = b;
b = b->next;
head = a;
} else
{
tmp = b->next;
b->next = a->next;
a->next = tmp;
c->next = b;
d->next = a;
tmp = a;
a = b;
b = tmp;
d = b;
b = b->next;
}
}
} else
{
d = b;
b = b->next;
}
}
c = a;
a = a->next;
}
}

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