From d21952804763145fc99ac1ec4ab8c81f2e191f6f Mon Sep 17 00:00:00 2001
From: Alka107 <78424521+Alka107@users.noreply.github.com>
Date: Thu, 28 Oct 2021 10:41:33 +0530
Subject: [PATCH] reverse

---
 0025/ReverseNode.py | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 0025/ReverseNode.py

diff --git a/0025/ReverseNode.py b/0025/ReverseNode.py
new file mode 100644
index 0000000..b0e7bbc
--- /dev/null
+++ b/0025/ReverseNode.py
@@ -0,0 +1,21 @@
+def reverseKGroup(self, head: ListNode, k: int) -> ListNode:
+    p = head
+    e = r = ListNode(None)
+
+	# find out the length of the list
+    n = 0
+    while head:
+        head = head.next
+        n += 1
+
+	# rearrange the nodes
+    for i in range(n // k):    # for every group
+        s = p                  # record the first node of a group that will soon become the last node of the reversed group
+        for _ in range(k):     # for every node in a group
+            t = p.next
+            p.next = e.next    # put the current node right before the head of the reversed group
+            e.next = p         # register p as the head of the reversed group
+            p = t              # visit the next node in the original list
+        e = s                  # update the end of the reversed group
+    e.next = p                 # append the tail to the end
+    return r.next