Update python code of stack.

codes/python/chapter_stack_and_queue/array_stack.py

@@ -4,46 +4,45 @@
 Author: Peng Chen ([email protected])
 '''
 
-import os.path as osp
-import sys
-
+import sys, os.path as osp
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
 """ 基于数组实现的栈 """
 class ArrayStack:
     def __init__(self):
-        self._stack = []
-        self._size = 0
+        self.__stack = []
 
     """ 获取栈的长度 """
     def size(self):
-        return self._size
+        return len(self.__stack)
 
     """ 判断栈是否为空 """
     def is_empty(self):
-        return self._stack == []
+        return self.__stack == []
 
     """ 入栈 """
     def push(self, item):
-        self._stack.append(item)
-        self._size += 1
+        self.__stack.append(item)
 
     """ 出栈 """
     def pop(self):
-        pop = self._stack.pop()
-        self._size -= 1
-        return pop
+        return self.__stack.pop()
 
     """ 访问栈顶元素 """
     def peek(self):
-        return self._stack[-1]
+        return self.__stack[-1]
 
     """ 访问索引 index 处元素 """
     def get(self, index):
-        return self._stack[index]
+        return self.__stack[index]
+
+    """ 返回列表用于打印 """
+    def toList(self):
+        return self.__stack
 
 
+""" Driver Code """
 if __name__ == "__main__":
     """ 初始化栈 """
     stack = ArrayStack()
@@ -54,20 +53,20 @@ def get(self, index):
     stack.push(2)
     stack.push(5)
     stack.push(4)
-    print("栈 stack = ", stack._stack)
+    print("栈 stack =", stack.toList())
 
     """ 访问栈顶元素 """
     peek = stack.peek()
-    print("栈顶元素 peek = ", peek)
+    print("栈顶元素 peek =", peek)
 
     """ 元素出栈 """
     pop = stack.pop()
-    print("出栈元素 pop = ", pop)
-    print("出栈后 stack = ", stack._stack)
+    print("出栈元素 pop =", pop)
+    print("出栈后 stack =", stack.toList())
 
     """ 获取栈的长度 """
     size = stack.size()
-    print("栈的长度 size = ", size)
+    print("栈的长度 size =", size)
 
     """ 判断是否为空 """
     isEmpty = stack.is_empty()

codes/python/chapter_stack_and_queue/linkedlist_stack.py

@@ -4,58 +4,58 @@
 Author: Peng Chen ([email protected])
 '''
 
-import os.path as osp
-import sys
-
+import sys, os.path as osp
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
 """ 基于链表实现的栈 """
 class LinkedListStack:
     def __init__(self):
-        self.head = None
+        self.__head = None
+        self.__size = 0
 
     """ 获取栈的长度 """
     def size(self):
-        cnt = 0
-        temp = self.head
-        while temp is not None:
-            temp = temp.next
-            cnt += 1
-        return cnt
+        return self.__size
 
     """ 判断栈是否为空 """
     def is_empty(self):
-        if not self.head.val and not self.head.next:
-            return True
-        return False
+        return not self.__head
 
     """ 入栈 """
     def push(self, val):
-        temp = ListNode(val)
-        temp.next = self.head
-        self.head = temp
+        node = ListNode(val)
+        node.next = self.__head
+        self.__head = node
+        self.__size += 1
 
     """ 出栈 """
     def pop(self):
-        pop = self.head.val
-        self.head = self.head.next
+        # 判空处理
+        if not self.__head: return None
+        pop = self.__head.val
+        self.__head = self.__head.next
+        self.__size -= 1
         return pop
 
     """ 访问栈顶元素 """
     def peek(self):
-        return self.head.val
-
-    def to_array(self):
-        stack = []
-        temp = self.head
-        while temp:
-            stack.append(temp.val)
-            temp = temp.next
-        stack.reverse()
-        return stack
-
-
+        # 判空处理
+        if not self.__head: return None
+        return self.__head.val
+
+    """ 转化为列表用于打印 """
+    def to_list(self):
+        arr = []
+        node = self.__head
+        while node:
+            arr.append(node.val)
+            node = node.next
+        arr.reverse()
+        return arr
+
+
+""" Driver Code """
 if __name__ == "__main__":
     """ 初始化栈 """
     stack = LinkedListStack()
@@ -66,20 +66,20 @@ def to_array(self):
     stack.push(2)
     stack.push(5)
     stack.push(4)
-    print("栈 stack = ", stack.to_array())
+    print("栈 stack =", stack.to_list())
 
     """ 访问栈顶元素 """
     peek = stack.peek()
-    print("栈顶元素 peek = ", peek)
+    print("栈顶元素 peek =", peek)
 
     """ 元素出栈 """
     pop = stack.pop()
-    print("出栈元素 pop = ", pop)
-    print("出栈后 stack = ", stack.to_array())
+    print("出栈元素 pop =", pop)
+    print("出栈后 stack =", stack.to_list())
 
     """ 获取栈的长度 """
     size = stack.size()
-    print("栈的长度 size = ", size)
+    print("栈的长度 size =", size)
 
     """ 判断是否为空 """
     isEmpty = stack.is_empty()

codes/python/chapter_stack_and_queue/stack.py

@@ -4,14 +4,15 @@
 Author: Peng Chen ([email protected])
 '''
 
-import os.path as osp
-import sys
-
+import sys, os.path as osp
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
+
+""" Driver Code """
 if __name__ == "__main__":
     """ 初始化栈 """
+    # Python 没有内置的栈类，可以把 list 当作栈来使用 
     stack = []
 
     """ 元素入栈 """
@@ -20,20 +21,20 @@
     stack.append(2)
     stack.append(5)
     stack.append(4)
-    print("栈 stack = ", stack)
+    print("栈 stack =", stack)
 
     """ 访问栈顶元素 """
     peek = stack[-1]
-    print("栈顶元素 peek = ", peek)
+    print("栈顶元素 peek =", peek)
 
     """ 元素出栈 """
     pop = stack.pop()
-    print("出栈元素 pop = ", pop)
-    print("出栈后 stack = ", stack)
+    print("出栈元素 pop =", pop)
+    print("出栈后 stack =", stack)
 
     """ 获取栈的长度 """
     size = len(stack)
-    print("栈的长度 size = ", size)
+    print("栈的长度 size =", size)
 
     """ 判断是否为空 """
-    isEmpty = (stack == [])
+    isEmpty = len(stack) == 0