Reverse a Linked List in groups of a given size

Data Structures and Algorithms Note

how I would do

For the purpose of reverse linked list, think about using stack first!

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
 
 
class LinkedList:
    def __init__(self): 
        self.head = None
        
    def push(self, new_data):
        new_node = Node(new_data)
        new_node.next = self.head
        self.head = new_node
    
    def printList(self): 
        temp = self.head 
        while temp: 
            print(temp.data)
            temp = temp.next
     def reverse(self, head, k):
        if head is None:
            return
 
        curr = head
        prev = None
        new_stack = []
        
        while curr is not None:
            count = 0
             
            # exit for loop when current is None or count >= k
            while curr is not None and count < k:
                new_stack.append(curr)
                curr = curr.next
                count += 1
                
            # pop element of stack one by one until stack is empty
            while new_stack:
                 
                # head node
                if prev is None:
                    self.head = prev = new_stack.pop()
                else:
                    prev.next = new_stack.pop()
                    prev = prev.next
                     
        # next of last element will point to None.
        prev.next = None

curr will stop at the first node of the next round until it reached the last node.next, which is None.

the element stored in the stack will be popped and linked as a set, when the stack is empty, continue the process for the next round.

when the second last.next = new_stack.pop(), which means the new_stack become empty, and prev are assign as the last Node.

when curr is None, stop the while loop and at the end, make the next of prev, which is the last Node point to None to end the linked list.

REFERENCE
https://www.geeksforgeeks.org/reverse-linked-list-groups-given-size-set-2/?ref=lbp