From 50c35b796c3adaf9a0d0c13fbe95e270d7b1464d Mon Sep 17 00:00:00 2001
From: Wenru Dong <dongwenru.aaron.shenyang@gmail.com>
Date: Mon, 8 Oct 2018 21:04:25 +0100
Subject: [PATCH] implementation of linked-list-based stack in python

---
 python/08_stack/linked_stack.py | 49 +++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 python/08_stack/linked_stack.py

diff --git a/python/08_stack/linked_stack.py b/python/08_stack/linked_stack.py
new file mode 100644
index 0000000..2329d21
--- /dev/null
+++ b/python/08_stack/linked_stack.py
@@ -0,0 +1,49 @@
+"""
+    Stack based upon linked list
+    基于链表实现的栈
+    
+    Author: Wenru
+"""
+
+from typing import Optional
+
+class Node:
+    
+    def __init__(self, data: int, next=None):
+        self._data = data
+        self._next = next
+    
+
+class LinkedStack:
+    """A stack based upon singly-linked list.
+    """
+    def __init__(self):
+        self._top: Node = None
+    
+    def push(self, value: int):
+        new_top = Node(value)
+        new_top._next = self._top
+        self._top = new_top
+    
+    def pop(self) -> Optional[int]:
+        if self._top:
+            value = self._top._data
+            self._top = self._top._next
+            return value
+    
+    def __repr__(self) -> str:
+        current = self._top
+        nums = []
+        while current:
+            nums.append(current._data)
+            current = current._next
+        return " ".join(f"{num}]" for num in nums)
+
+if __name__ == "__main__":
+    stack = LinkedStack()
+    for i in range(9):
+        stack.push(i)
+    print(stack)
+    for _ in range(3):
+        stack.pop()
+    print(stack)
\ No newline at end of file