[jylee2033] WEEK 07 solutions

reverse-linked-list/jylee2033.py

@@ -0,0 +1,27 @@
+# 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]:
+        # Handle empty list
+        if head is None:
+            return head
+
+        prev = None
+        cur = head # Start from the head node
+
+        # Traverse until the last node
+        while cur.next is not None:
+            nxt = cur.next # Store next node
+            cur.next = prev # Reverse the link
+            prev = cur # Move prev forward
+            cur = nxt # Move cur forward
+
+        # Handle the last node
+        cur.next = prev
+        return cur
+
+# Time Complexity: O(n)
+# Space Complexity: O(1)