/*
* This function reverses a linked list recursively .
*/
void reverseRecursive(struct node **head){
struct node *first;
struct node *rest;
/* empty list */
if(*head == NULL){
return ;
}
first = *head ;
rest = first->next;
/* List has only one node */
if(rest == NULL){
return ;
}
/* reverse the rest list and put the first element at the end */
reverseRecursive(&rest) ;
first->next->next = first ;
first->next = NULL ;
/* fix the head pointer */
*head = rest ;
}
void reverseRecursive(struct node ** head)
{
struct node * first;
struct node * rest;
/*zero nodes*/
if(*head == NULL)
return;
first = *head;
rest = first->next;
/*Single node*/
if(rest == NULL)
return;
/*Recursion for the rest*/
reverseRecursive(&rest);
//Switch the link
first->next->next = first;
first->next = NULL;
*head = rest;
}
int main()
{
int arr[] = {3, 4, 5, 6, 7};
std::vector<int> array(arr, arr+sizeof(arr)/sizeof(int));
struct node * head = new struct node;
createLinkedList(array, &head);
displayList(head);
// reverse(&head);
reverseRecursive(&head);
displayList(head);
return 0;
}
int main(void) {
struct node *head = NULL ;
insertFirst(&head, 10);
insertFirst(&head, 22);
insertFirst(&head, 35);
insertFirst(&head, 75);
printf("Original Linked list \n");
printList(head);
reverseRecursive(&head);
printf("\nReversed Linked list \n");
printList(head);
getchar();
}
static void reverseStringRecursive(std::string& string) {
int length = string.size();
reverseRecursive(string, 0, length - 1);
}
/**
* Time complexity: O(n)
* Space complexity: O(n)
* where n is the maximum recursion depth
*/
static void reverseRecursive(std::string& string, int begin, int end) {
if (begin < end) {
std::swap(string[begin],string[end]);
reverseRecursive(string, ++begin, --end);
}
}
