From 714d6aaab32948f91528c574ef676b4cf1b39ce1 Mon Sep 17 00:00:00 2001
From: parth <parthkhandenath123@gmail.com>
Date: Mon, 2 Oct 2023 01:00:19 +0530
Subject: [PATCH 1/2] reverse linked list of groups of given size

---
 .../reverse_in_group_of_given_size.py         | 126 ++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 data_structures/linked_list/reverse_in_group_of_given_size.py

diff --git a/data_structures/linked_list/reverse_in_group_of_given_size.py b/data_structures/linked_list/reverse_in_group_of_given_size.py
new file mode 100644
index 000000000000..3df2e27addd3
--- /dev/null
+++ b/data_structures/linked_list/reverse_in_group_of_given_size.py
@@ -0,0 +1,126 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+
+@dataclass
+class Node:
+    data: int
+    nextt: Node | None = None
+
+
+def insert_node(head: Node | None, data: int) -> Node:
+    """
+    Insert a new node at the end of a linked list and return the new head.
+    >>> head = insert_node(None, 1)
+    >>> head = insert_node(head, 2)
+    >>> head = insert_node(head, 3)
+    >>> print_linked_list(head)
+    1->2->3
+    """
+    new_node = Node(data)
+    # If the linked list is empty, the new_node becomes the head
+    if head is None:
+        return new_node
+
+    temp_node = head
+    while temp_node.nextt is not None:
+        temp_node = temp_node.nextt
+
+    temp_node.nextt = new_node  # type: ignore
+    return head
+
+
+def length_of_linked_list(head: Node | None) -> int:
+    """
+    find length of linked list
+    >>> head = insert_node(None, 10)
+    >>> head = insert_node(head, 9)
+    >>> head = insert_node(head, 8)
+    >>> length_of_linked_list(head)
+    3
+    """
+    length = 0
+    while head is not None:
+        length += 1
+        head = head.nextt
+    return length
+
+
+def print_linked_list(head: Node | None) -> None:
+    """
+    print the entire linked list
+    >>> head = insert_node(None, 1)
+    >>> head = insert_node(head, 2)
+    >>> head = insert_node(head, 3)
+    >>> print_linked_list(head)
+    1->2->3
+    """
+    if head is not None:
+        while head.nextt is not None:
+            print(head.data, end="->")
+            head = head.nextt
+        print(head.data)
+
+
+def reverse_k_nodes(head: Node | None, k: int) -> Node | None:
+    """
+    reverse nodes within groups of size k
+    >>> k = 3
+    >>> head = insert_node(None, 1)
+    >>> head = insert_node(head, 2)
+    >>> head = insert_node(head, 3)
+    >>> head = insert_node(head, 4)
+    >>> head = insert_node(head, 5)
+    >>> new_head = reverse_k_nodes(head, 2)
+    >>> print_linked_list(new_head)
+    2->1->4->3->5
+    """
+    if head is None or head.nextt is None:
+        return head
+
+    length = length_of_linked_list(head)
+
+    dummy_head = Node(0)
+    dummy_head.nextt = head
+
+    previous_node = dummy_head
+
+    while length >= k:
+        assert previous_node
+        current_node = previous_node.nextt
+        assert current_node
+        next_node = current_node.nextt
+        for _ in range(1, k):
+            assert next_node, current_node
+            current_node.nextt = next_node.nextt
+            assert previous_node
+            next_node.nextt = previous_node.nextt
+            assert previous_node
+            previous_node.nextt = next_node
+            assert current_node
+            next_node = current_node.nextt
+        previous_node = current_node
+        length -= k
+    assert dummy_head
+    return dummy_head.nextt
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()
+
+    k = 2
+    head = insert_node(None, 1)
+    head = insert_node(head, 2)
+    head = insert_node(head, 3)
+    head = insert_node(head, 4)
+    head = insert_node(head, 5)
+
+    print("Original Linked List: ", end="")
+    print_linked_list(head)
+    print("After Reversal of k nodes: ", end="")
+    new_head = reverse_k_nodes(head, k)
+    print_linked_list(new_head)
+    print()

From 4c0207e2ffed774e08eafbcfd1435d71ff21ac7d Mon Sep 17 00:00:00 2001
From: parth <parthkhandenath123@gmail.com>
Date: Mon, 2 Oct 2023 01:09:18 +0530
Subject: [PATCH 2/2] minor changes as suggested

---
 .../linked_list/reverse_in_group_of_given_size.py        | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/data_structures/linked_list/reverse_in_group_of_given_size.py b/data_structures/linked_list/reverse_in_group_of_given_size.py
index 3df2e27addd3..468421ebd012 100644
--- a/data_structures/linked_list/reverse_in_group_of_given_size.py
+++ b/data_structures/linked_list/reverse_in_group_of_given_size.py
@@ -63,10 +63,9 @@ def print_linked_list(head: Node | None) -> None:
         print(head.data)
 
 
-def reverse_k_nodes(head: Node | None, k: int) -> Node | None:
+def reverse_k_nodes(head: Node | None, group_size: int) -> Node | None:
     """
     reverse nodes within groups of size k
-    >>> k = 3
     >>> head = insert_node(None, 1)
     >>> head = insert_node(head, 2)
     >>> head = insert_node(head, 3)
@@ -86,12 +85,12 @@ def reverse_k_nodes(head: Node | None, k: int) -> Node | None:
 
     previous_node = dummy_head
 
-    while length >= k:
+    while length >= group_size:
         assert previous_node
         current_node = previous_node.nextt
         assert current_node
         next_node = current_node.nextt
-        for _ in range(1, k):
+        for _ in range(1, group_size):
             assert next_node, current_node
             current_node.nextt = next_node.nextt
             assert previous_node
@@ -101,7 +100,7 @@ def reverse_k_nodes(head: Node | None, k: int) -> Node | None:
             assert current_node
             next_node = current_node.nextt
         previous_node = current_node
-        length -= k
+        length -= group_size
     assert dummy_head
     return dummy_head.nextt