typedef struct list_s {int data;struct list_s *next;
} list_t;

 1 static int get_length(list_t *head)
 2 {
 3         int len = 0;
 4         for (list_t *p = head; p != NULL; p = p->next)
 5                 len++;
 6         return len;
 7 }
 8
 9 void reverse_singly_linked_list(list_t **head)
10 {
11         if (*head == NULL)
12                 return;
13
14         int len = get_length(*head);
15         if (len < 2)
16                 return;
17
18         list_t **aux = (list_t **)malloc(sizeof (list_t *) * len);
19         if (aux == NULL) /* error */
20                 return;
21
22         /* save addr of per node to aux[] */
23         int index = 0;
24         for (list_t *p = *head; p != NULL; p = p->next) {
25                 aux[len-1-index] = p;
26                 index++;
27         }
28
29         /* rebuild the singly linked list by walking aux[] */
30         *head = aux[0];
31         for (int i = 0; i < len-1; i++)
32                 aux[i]->next = aux[i+1];
33         aux[len-1]->next = NULL;
34
35         free(aux);
36 }

 1 void reverse_singly_linked_list(list_t **head)
 2 {
 3         list_t *newhead = NULL;
 4         list_t *this = *head;
 5         list_t *prev = NULL;
 6
 7         while (this != NULL) {
 8                 /*
 9                  * If this->next is NULL, this is the tail node, which should
10                  * be the new head
11                  */
12                 if (this->next == NULL)
13                         newhead = this;
14
15                 /*
16                  * ListIn:  prevNode -> thisNode -> nextNode
17                  * ListOut: prevNode <- thisNode <- nextNode
18                  *          1. thisNode->next = prevNode;
19                  *          2.       prevNode = thisNode;
20                  *          3.       thisNode = thisNode->next;
21                  */
22                 list_t *next = this->next; /* a. save the next */
23                 this->next = prev;         /* b. reverse */
24                 prev = this;               /* c. move prev forward */
25                 this = next;               /* d. move this forward */
26         }
27
28         *head = newhead;
29 }