added daily challenge

Author: Pasindu-Vishmika

206. Reverse Linked List.py

@@ -0,0 +1,17 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        prev_node = None
+        current_node = head
+
+        while current_node is not None:
+            next_node = current_node.next
+            current_node.next = prev_node
+            prev_node = current_node
+            current_node = next_node
+
+        return prev_node