reorganize dir

Signed-off-by: Mia Steinkirch <mia.steinkirch@gmail.com>

ebook_src/abstract_structures/stacks/linked_stack.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+""" 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.head = None
+
+    def isEmpty(self):
+        return not bool(self.head)
+
+    def push(self, item):
+        self.head = Node(item, self.head)
+
+
+    def pop(self):
+        if self.head:
+            node = self.head
+            self.head = node.pointer
+            return node.value
+        else:
+            print('Stack is empty.')
+
+
+    def peek(self):
+        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__':
+    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()