Reverse_Linked_list

class ListNode:
    def __init__(self, value=0, next=None):
        self.value = value
        self.next = next

def reverse_linked_list(head, k):
    current = head
    prev = None
    next_node = None
    count = 0

    # Count the number of nodes in the current group
    temp = head
    while temp is not None and count < k:
        temp = temp.next
        count += 1

    # If the number of nodes in the group is less than k, no need to reverse
    if count < k:
        return head

    # Reverse the nodes in the current group
    while count > 0:
        next_node = current.next
        current.next = prev
        prev = current
        current = next_node
        count -= 1

    # Recursively reverse the rest of the linked list
    if next_node is not None:
        head.next = reverse_linked_list(next_node, k)

    return prev

def print_linked_list(head):
    current = head
    while current is not None:
        print(current.value, end=" -> ")
        current = current.next
    print("None")

# Example usage:
# Create a linked list: 1 -> 2 -> 3 -> 4 -> 5
head = ListNode(1, ListNode(2, ListNode(3, ListNode(4, ListNode(5)))))

# Reverse in groups of k = 3
new_head = reverse_linked_list(head, 3)

# Print the reversed linked list
print_linked_list(new_head)