week 7: Reverse Linked List

Author: prograsshopper

reverse-linked-list/prograsshopper.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 reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        # time complexity: O(n) / memory complexity: O(n)
+        stack = []
+        current = head
+        while current:
+            stack.append(current.val)
+            current = current.next
+
+        dummy_head = ListNode()
+        current = dummy_head
+        while stack:
+            current.next = ListNode(val=stack.pop(), next=None)
+            current = current.next
+        return dummy_head.next