Update solution 876 [Python3]

Author: chakyam

solution/876.Middle of the Linked List/Solution.py

@@ -0,0 +1,23 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    def middleNode(self, head):
+        """
+        :type head: ListNode
+        :rtype: ListNode
+        """
+        if not head:
+            return None
+        if not head.next:
+            return head
+        fast=head
+        slow=head
+        while fast.next:
+            fast=fast.next.next
+            slow=slow.next
+            if not fast or not fast.next:
+                return slow