fixes

src/abstract_structures/adt/queues/linked_queue.py

@@ -0,0 +1,61 @@
+#!/usr/bin/python3
+# mari von steinkirch @2013
+# steinkirch at gmail
+
+class Node(object):
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+        
+
+class LinkedQueue(object):
+    ''' Queue acts as a container for nodes (objects) that are inserted and removed according FIFO'''
+    def __init__(self):
+        self.front = None
+        self.back = None
+
+    def isEmpty(self):
+        return bool(self.front)
+
+    def dequeue(self):
+        if self.front:
+            value = self.front.value
+            self.front = self.front.next
+            return value
+        raise Exception('Queue is empty, cannot dequeue.')
+
+    def enqueue(self, value):
+        node = Node(value)
+        if self.front:
+            self.back.next = node
+            self.back = node
+        else:
+            self.front = node
+            self.back = node
+        return True
+
+    def size(self):
+        node = self.front
+        num_nodes = 1
+        while node.next:
+            num_nodes += 1
+            node = node.next
+        return num_nodes
+
+    def peek(self):
+        return self.front.value
+
+
+def main():
+    queue = LinkedQueue()
+    queue.enqueue(1)
+    queue.enqueue(2)
+    queue.enqueue(3)
+    print(queue.size())    
+    print(queue.peek())   
+    print(queue.dequeue())  
+    print(queue.peek())    
+
+
+if __name__ == '__main__':
+    main()