09_singlyLL_rotate.py

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None


class SinglyLinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)

        if self.head is None:
            self.head = new_node
            return

        last_node = self.head
        while last_node.next:
            last_node = last_node.next
        last_node.next = new_node

    def prepend(self, data):
        new_node = Node(data)

        if self.head is None:
            self.head = new_node
            return

        cur_node = self.head
        self.head = new_node
        new_node.next = cur_node

    def print_list(self):
        cur_node = self.head
        while cur_node:
            print(cur_node.data)
            cur_node = cur_node.next

    def rotate_list(self, k):

        p = self.head
        q = self.head
        prev = None
        count = 0

        while p and count < k:
            prev = p
            p = p.next
            q = q.next
            count += 1
        p = prev

        while q:
            prev = q
            q = q.next
        q = prev
        
        cur = self.head
        q.next = cur
        self.head = p.next
        p.next = None


    
llist = SinglyLinkedList()
llist.append(1)
llist.append(2)
llist.append(3)
llist.append(4)
llist.append(5)
llist.append(6)
llist.append(7)
llist.append(8)

llist.print_list()
print("\n")

llist.rotate_list(4)
llist.print_list()