Create 206-reverse_linked_list.py

Author: stevestar888

206-reverse_linked_list.py

@@ -0,0 +1,32 @@
+"""
+Reverse a singly linked list.
+
+Runtime: 28 ms, faster than 40.74% of Python online submissions for Reverse Linked List.
+Memory Usage: 14.7 MB, less than 25.93% of Python online submissions for Reverse Linked List.
+"""
+
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+
+class Solution(object):
+    def reverseList(self, head):
+        """
+        :type head: ListNode
+        :rtype: ListNode
+        """        
+        prev_node = None
+        curr_node = head
+        
+        while curr_node: #while our head points to something
+            next_node = curr_node.next
+            curr_node.next = prev_node
+            
+            #advance to next node
+            prev_node = curr_node
+            curr_node = next_node
+            
+        #curr_node is None, so return prev_node
+        return prev_node