feat: Solve reorder-list problem

Author: hu6r1s

reorder-list/hu6r1s.py

@@ -0,0 +1,26 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reorderList(self, head: Optional[ListNode]) -> None:
+        """
+        Do not return anything, modify head in-place instead.
+        """
+        stack = []
+        node = head
+        while node:
+            stack.append(node)
+            node = node.next
+
+        node = dummy = ListNode(-1)
+        for i in range(len(stack)):
+            if i % 2:
+                node.next = stack.pop()
+            else:
+                node.next = head
+                head = head.next
+            node = node.next
+        node.next = None
+        return dummy.next