fix few details, stacks

src/abstract_structures/stacks/linked_stack.py

@@ -1,52 +1,73 @@
-#!/usr/bin/python3
-# mari von steinkirch @2013
-# steinkirch at gmail
+#!/usr/bin/python
 
-class Node:
-    def __init__(self, value=None):
-        self.value = value 
-        self.next = None
+__author__ = "Mari Wahl"
+__email__ = "marina.w4hl@gmail.com"
 
-class StackwithNodes:
-    ''' Define a Stack with nodes'''
+
+""" A stack made of linked list"""
+
+
+
+class Node(object):
+    def __init__(self, value=None, pointer=None):
+        self.value = value
+        self.pointer = pointer
+
+
+class Stack(object):
     def __init__(self):
-        self.top = None
+        self.head = None
 
     def isEmpty(self):
-        return bool(self.top)
+        return not bool(self.head)
+
+    def push(self, item):
+        self.head = Node(item, self.head)
+
 
     def pop(self):
-        node = self.top
-        self.top = node.next
-        return node.value
+        if self.head:
+            node = self.head
+            self.head = node.pointer
+            return node.value
+        else:
+            print('Stack is empty.')
 
-    def push(self, value):
-        node = Node(value)
-        node.next = self.top
-        self.top = node
-
-    def size(self):
-        node = self.top
-        if node not None: num_nodes = 1
-        else: return 0
-        while node.next:
-            num_nodes += 1
-            node = node.next
-        return num_nodes
 
     def peek(self):
-        return self.top.value
-        
-        
-def main():
-    stack = StackwithNodes()
-    stack.push(1)
-    stack.push(2)
-    stack.push(3)
-    print(stack.size())    
-    print(stack.peek())   
-    print(stack.pop())  
-    print(stack.peek())    
+        if self.head:
+            return self.head.value
+        else:
+            print('Stack is empty.')
+
+
+    def size(self):
+        node = self.head
+        count = 0
+        while node:
+            count +=1
+            node = node.pointer
+        return count
+
+
+    def _printList(self):
+        node = self.head
+        while node:
+            print(node.value)
+            node = node.pointer
+
+
 
 if __name__ == '__main__':
-    main()
+    stack = Stack()
+    print("Is the stack empty? ", stack.isEmpty())
+    print("Adding 0 to 10 in the stack...")
+    for i in range(10):
+        stack.push(i)
+    stack._printList()
+    print("Stack size: ", stack.size())
+    print("Stack peek : ", stack.peek())
+    print("Pop...", stack.pop())
+    print("Stack peek: ", stack.peek())
+    print("Is the stack empty? ", stack.isEmpty())
+    stack._printList()