From b8beb67e6b958d64b6f1816bd5b2f254982932b4 Mon Sep 17 00:00:00 2001
From: Chris Cooper <christopher.p.cooper@gmail.com>
Date: Sun, 3 Sep 2023 15:19:38 -0700
Subject: [PATCH 1/3] Use recursion to minimize the code and it is surprisingly
 fast.

---
 python/0021-merge-two-sorted-lists.py | 27 ++++++++-------------------
 1 file changed, 8 insertions(+), 19 deletions(-)

diff --git a/python/0021-merge-two-sorted-lists.py b/python/0021-merge-two-sorted-lists.py
index 9f6cd8044..2626af4e0 100644
--- a/python/0021-merge-two-sorted-lists.py
+++ b/python/0021-merge-two-sorted-lists.py
@@ -4,22 +4,11 @@
 #         self.val = val
 #         self.next = next
 class Solution:
-    def mergeTwoLists(self, list1: ListNode, list2: ListNode) -> ListNode:
-        dummy = ListNode()
-        tail = dummy
-
-        while list1 and list2:
-            if list1.val < list2.val:
-                tail.next = list1
-                list1 = list1.next
-            else:
-                tail.next = list2
-                list2 = list2.next
-            tail = tail.next
-
-        if list1:
-            tail.next = list1
-        elif list2:
-            tail.next = list2
-
-        return dummy.next
+    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
+        if not list1:
+            return list2
+        if not list2:
+            return list1
+        lil, big = (list1, list2) if list1.val < list2.val else (list2, list1)
+        lil.next = self.mergeTwoLists(lil.next, big)
+        return lil

From cb95cde111e4c79532fd2228c26ba02abdead852 Mon Sep 17 00:00:00 2001
From: Chris Cooper <christopher.p.cooper@gmail.com>
Date: Mon, 4 Sep 2023 09:00:32 -0700
Subject: [PATCH 2/3] Add Iterative along with Recursive solution

---
 python/0021-merge-two-sorted-lists.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/python/0021-merge-two-sorted-lists.py b/python/0021-merge-two-sorted-lists.py
index 2626af4e0..edbf54db0 100644
--- a/python/0021-merge-two-sorted-lists.py
+++ b/python/0021-merge-two-sorted-lists.py
@@ -3,6 +3,8 @@
 #     def __init__(self, val=0, next=None):
 #         self.val = val
 #         self.next = next
+
+# Recursive
 class Solution:
     def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
         if not list1:
@@ -12,3 +14,21 @@ def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) ->
         lil, big = (list1, list2) if list1.val < list2.val else (list2, list1)
         lil.next = self.mergeTwoLists(lil.next, big)
         return lil
+
+# Iterative
+class Solution:
+    def mergeTwoLists(self, list1: ListNode, list2: ListNode) -> ListNode:
+        dummy = node = ListNode()
+
+        while list1 and list2:
+            if list1.val < list2.val:
+                node.next = list1
+                list1 = list1.next
+            else:
+                node.next = list2
+                list2 = list2.next
+            node = node.next
+
+        node.next = list1 or list2
+
+        return dummy.next

From 3e8f1a23cb963f57f1cd11f5c35e689f1c35bedd Mon Sep 17 00:00:00 2001
From: Chris Cooper <christopher.p.cooper@gmail.com>
Date: Mon, 4 Sep 2023 09:04:29 -0700
Subject: [PATCH 3/3] Moved the original solution to the top and the new one to
 the bottom.

---
 python/0021-merge-two-sorted-lists.py | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/python/0021-merge-two-sorted-lists.py b/python/0021-merge-two-sorted-lists.py
index edbf54db0..e08821bda 100644
--- a/python/0021-merge-two-sorted-lists.py
+++ b/python/0021-merge-two-sorted-lists.py
@@ -4,17 +4,6 @@
 #         self.val = val
 #         self.next = next
 
-# Recursive
-class Solution:
-    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
-        if not list1:
-            return list2
-        if not list2:
-            return list1
-        lil, big = (list1, list2) if list1.val < list2.val else (list2, list1)
-        lil.next = self.mergeTwoLists(lil.next, big)
-        return lil
-
 # Iterative
 class Solution:
     def mergeTwoLists(self, list1: ListNode, list2: ListNode) -> ListNode:
@@ -32,3 +21,14 @@ def mergeTwoLists(self, list1: ListNode, list2: ListNode) -> ListNode:
         node.next = list1 or list2
 
         return dummy.next
+    
+# Recursive
+class Solution:
+    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
+        if not list1:
+            return list2
+        if not list2:
+            return list1
+        lil, big = (list1, list2) if list1.val < list2.val else (list2, list1)
+        lil.next = self.mergeTwoLists(lil.next, big)
+        return lil