linkedlistreverse

#include <bits/stdc++.h>
using namespace std;

/* Link list node */
class Node {
public:
	int data;
	Node* next;
};

/* Reverses the linked list in groups
of size k and returns the pointer
to the new head node. */
Node* reverse(Node* head, int k)
{
	// base case
	if (!head)
		return NULL;
	Node* current = head;
	Node* next = NULL;
	Node* prev = NULL;
	int count = 0;

	/*reverse first k nodes of the linked list */
	while (current != NULL && count < k) {
		next = current->next;
		current->next = prev;
		prev = current;
		current = next;
		count++;
	}

	/* next is now a pointer to (k+1)th node
	Recursively call for the list starting from current.
	And make rest of the list as next of first node */
	if (next != NULL)
		head->next = reverse(next, k);

	/* prev is new head of the input list */
	return prev;
}

void push(Node** head_ref, int new_data)
{
	/* allocate node */
	Node* new_node = new Node();


	new_node->data = new_data;

	new_node->next = (*head_ref);

	(*head_ref) = new_node;
}

/* Function to print linked list */
void printList(Node* node)
{
	while (node != NULL) {
		cout << node->data << " ";
		node = node->next;
	}
}



int main()
{
	/* Start with the empty list */
	Node* head = NULL;


	push(&head, 9);
	push(&head, 8);
	push(&head, 7);
	push(&head, 6);
	push(&head, 5);
	push(&head, 4);
	push(&head, 3);
	push(&head, 2);
	push(&head, 1);

	cout << "Given linked list \n";
	printList(head);
	head = reverse(head, 3);

	cout << "\nReversed Linked list \n";
	printList(head);

	return (0);
}