bool is_palin(struct node *head)
{
if (head == NULL || head->next == NULL)
return true;
struct node *slow = head;
struct node *fast = head->next;
struct node *prev_to_slow = NULL;
while (fast && fast->next) {
prev_to_slow = slow;
slow = slow->next;
fast = fast->next->next;
}
if (!fast) {
struct node *second = slow->next;
prev_to_slow->next = NULL;
reverse_recursive(&second);
bool result = compare_lists(head, second);
reverse_recursive(&second);
prev_to_slow->next = slow;
return result;
// the list is of odd lenth, should skip the middle element while comparing.
} else {
struct node *second = slow->next;
slow->next = NULL;
reverse_recursive(&second);
bool result = compare_lists(head, second);
reverse_recursive(&second);
slow->next = second;
return result;
}
return false;
}
int main(){
NODE *head = NULL;
int choice;
struct node *cur = malloc(sizeof(NODE));
printf("Enter the data");
scanf("%d", &cur->data);
cur->next = head;
head = cur;
do{
printf("Enter 1 to insert, 2 for display 3.to reverse,0.exit\n");
scanf("%d", &choice);
switch(choice){
case 0:
exit(0);
break;
case 1:
insert(&head);
break;
case 2:
display(head);
break;
case 3:
reverse_recursive(&head);
break;
}
}while(choice <= 3);
return 0;
}
data_t*
reverse_recursive(data_t *head) {
data_t *tmp;
if (!head || !head->next) {
return head;
}
tmp = reverse_recursive(head->next);
head->next->next = head;
head->next = NULL;
return tmp;
}
void reverse_recursive(struct node **head)
{
if (*head == NULL)
return;
struct node *result = (*head)->next;
if (result == NULL)
return ;
reverse_recursive(&result);
(*head)->next->next = *head;
(*head)->next = NULL;
*head = result;
}
reverse_recursive (Node *cur, Node *prev, Node **Head)
{
if (cur->next == NULL) {
*Head = cur;
cur->next = prev;
return;
}
Node *next = cur->next;
cur->next = prev;
reverse_recursive (next, cur, Head);
}
void reverse_recursive(struct node** head)
{
struct node* first;
struct node* remain;
if (*head == NULL)
return;
first = *head;
remain = first->next;
if (remain == NULL)
return;
reverse_recursive(&remain);
first->next->next = first;
first->next = NULL;
*head = remain;
}
void reverse_recursive(node *head)
{
node *last=head,*slast;
if(head->next==NULL)
{
return;
}
else
{
while(last->next!=NULL)
{
slast=last;
last=last->next;
}
slast->next=NULL;
last->next=slast;
reverse_recursive(head);
}
return;
}
