solution: reverse-linked-list

Author: wozlsla

reverse-linked-list/wozlsla.py

@@ -0,0 +1,49 @@
+"""
+# Complexity
+time : O(N)
+space : O(1) / O(N)
+"""
+
+# 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 = None
+        curr = head
+
+        while curr:
+            nxt = curr.next
+            curr.next = prev
+            prev = curr
+            curr = nxt
+
+        return prev
+
+
+""" Stack
+class Solution:
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+
+        stack = []
+        node = head
+
+        while node:
+            stack.append(node)
+            node = node.next
+
+        dummy = ListNode(-1)
+        node = dummy
+
+        while stack:
+            node.next = stack.pop()
+            node = node.next
+
+        node.next = None
+        return dummy.next
+"""