reorganize dir

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

ebook_src/abstract_structures/queues/linked_queue.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+''' Queue acts as a container for nodes (objects) that are inserted and removed according FIFO'''
+
+
+class Node(object):
+    def __init__(self, value=None, pointer=None):
+        self.value = value
+        self.pointer = None
+
+
+class LinkedQueue(object):
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+
+    def isEmpty(self):
+        return not bool(self.head)
+
+
+    def dequeue(self):
+        if self.head:
+            value = self.head.value
+            self.head = self.head.pointer
+            return value
+        else:
+            print('Queue is empty, cannot dequeue.')
+
+
+    def enqueue(self, value):
+        node = Node(value)
+        if not self.head:
+            self.head = node
+            self.tail = node
+        else:
+            if self.tail:
+                self.tail.pointer = node
+            self.tail = node
+
+
+    def size(self):
+        node = self.head
+        num_nodes = 0
+        while node:
+                num_nodes += 1
+                node = node.pointer
+        return num_nodes
+
+
+    def peek(self):
+        return self.head.value
+
+
+    def _print(self):
+        node = self.head
+        while node:
+            print(node.value)
+            node = node.pointer
+
+
+
+
+if __name__ == '__main__':
+    queue = LinkedQueue()
+    print("Is the queue empty? ", queue.isEmpty())
+    print("Adding 0 to 10 in the queue...")
+    for i in range(10):
+        queue.enqueue(i)
+    print("Is the queue empty? ", queue.isEmpty())
+    queue._print()
+
+    print("Queue size: ", queue.size())
+    print("Queue peek : ", queue.peek())
+    print("Dequeue...", queue.dequeue())
+    print("Queue peek: ", queue.peek())
+    queue._print()
+