Implement queue using stack

Author: AnushreeBagchi

implement_queue_using_stack.py

@@ -0,0 +1,47 @@
+class Stack:
+    def __init__(self):
+        self.items = []
+    def size(self):
+        return len(self.items)
+    def push(self, value):
+        self.items.append(value)
+    def pop(self):
+        if self.size == 0:
+            return None
+        return self.items.pop()
+
+class Queue:
+    def __init__(self):
+        self.instorage = Stack()
+        self.outstorage = Stack()
+
+    def size(self):
+        return self.instorage.size() + self.outstorage.size()
+    def enqueue(self, value):
+        self.instorage.push(value)
+    def dequeue(self):
+        if not self.outstorage.items:
+            while self.instorage.items:
+                self.outstorage.push(self.instorage.pop())
+            return self.outstorage.pop()
+
+q = Queue()
+q.enqueue(1)
+q.enqueue(2)
+q.enqueue(3)
+
+# Test size
+print ("Pass" if (q.size() == 3) else "Fail")
+
+# Test dequeue
+print ("Pass" if (q.dequeue() == 1) else "Fail")
+
+# Test enqueue
+q.enqueue(4)
+print ("Pass" if (q.dequeue() == 2) else "Fail")
+print ("Pass" if (q.dequeue() == 3) else "Fail")
+print ("Pass" if (q.dequeue() == 4) else "Fail")
+q.enqueue(5)
+print ("Pass" if (q.size() == 1) else "Fail") 
+    
+