Create middle_linked_list.py

finds the middle node of linked list in O(n) time

middle_linked_list.py

@@ -0,0 +1,20 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def middleNode(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        temp = head
+        middle = head
+        index = 0
+        prev = 0.5
+        if temp.next == None:
+            return temp
+        while temp != None:
+            temp = temp.next
+            if prev % 1 == 0:
+                middle = middle.next
+            index += 1
+            prev += 0.5
+        return middle