From 9fefcd12f05c58c66c5032ebe0b4c94dc7ddd2a3 Mon Sep 17 00:00:00 2001
From: Donne Martin <donne.martin@gmail.com>
Date: Sat, 23 May 2015 17:04:03 -0400
Subject: [PATCH] Updated problem solution to use stack's is_empty() method
 rather than a similar method that used to be in QueueFromStacks.

---
 stacks-queues/queue-from-stacks.ipynb | 45 ++++-----------------------
 1 file changed, 6 insertions(+), 39 deletions(-)

diff --git a/stacks-queues/queue-from-stacks.ipynb b/stacks-queues/queue-from-stacks.ipynb
index c08afe0..2c0734f 100644
--- a/stacks-queues/queue-from-stacks.ipynb
+++ b/stacks-queues/queue-from-stacks.ipynb
@@ -85,7 +85,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": null,
    "metadata": {
     "collapsed": true
    },
@@ -96,7 +96,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": null,
    "metadata": {
     "collapsed": false
    },
@@ -107,52 +107,28 @@
     "        self.left_stack = Stack()\n",
     "        self.right_stack = Stack()\n",
     "\n",
-    "    def is_stack_empty(self, stack):\n",
-    "        return stack.peek() is None\n",
-    "\n",
     "    def shift_stacks(self, source, destination):\n",
     "        while source.peek() is not None:\n",
     "            destination.push(source.pop())\n",
     "\n",
     "    def enqueue(self, data):\n",
-    "        if self.is_stack_empty(self.left_stack) and not self.is_stack_empty(self.right_stack):\n",
+    "        if self.left_stack.is_empty() and not self.right_stack.is_empty():\n",
     "            self.shift_stacks(self.right_stack, self.left_stack)\n",
     "        self.left_stack.push(data)\n",
     "\n",
     "    def dequeue(self):\n",
-    "        if self.is_stack_empty(self.right_stack) and not self.is_stack_empty(self.left_stack):\n",
+    "        if self.right_stack.is_empty() and not self.left_stack.is_empty():\n",
     "            self.shift_stacks(self.left_stack, self.right_stack)\n",
     "        return self.right_stack.pop()"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": null,
    "metadata": {
     "collapsed": false
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "Dequeue on empty stack\n",
-      "None\n",
-      "Enqueue on empty stack\n",
-      "Enqueue on non-empty stack\n",
-      "Multiple enqueue in a row\n",
-      "Dequeue on non-empty stack\n",
-      "Dequeue after an enqueue\n",
-      "0\n",
-      "Multiple dequeue in a row\n",
-      "1\n",
-      "2\n",
-      "Enqueue after a dequeue\n",
-      "5\n",
-      "None\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "print('Dequeue on empty stack')\n",
     "queue = QueueFromStacks()\n",
@@ -173,15 +149,6 @@
     "queue.enqueue(5)\n",
     "print(queue.dequeue())"
    ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {
-    "collapsed": true
-   },
-   "outputs": [],
-   "source": []
   }
  ],
  "metadata": {