Fix check balance challenge spacing

Author: donnemartin

graphs_trees/check_balance/check_balance_solution.ipynb

@@ -104,24 +104,24 @@
    "source": [
     "class BstBalance(Bst):\n",
     "\n",
-    "    def _check_height(self, node):\n",
+    "    def _check_balance(self, node):\n",
     "        if node is None:\n",
     "            return 0\n",
-    "        left_height = self._check_height(node.left)\n",
+    "        left_height = self._check_balance(node.left)\n",
     "        if left_height == -1:\n",
     "            return -1\n",
-    "        right_height = self._check_height(node.right)\n",
+    "        right_height = self._check_balance(node.right)\n",
     "        if right_height == -1:\n",
     "            return -1\n",
-    "        diff = abs(left_height-right_height)\n",
+    "        diff = abs(left_height - right_height)\n",
     "        if diff > 1:\n",
     "            return -1\n",
     "        return 1 + max(left_height, right_height)\n",
     "\n",
     "    def check_balance(self):\n",
     "        if self.root is None:\n",
     "            raise TypeError('root cannot be None')\n",
-    "        height = self._check_height(self.root)\n",
+    "        height = self._check_balance(self.root)\n",
     "        return height != -1"
    ]
   },
@@ -235,7 +235,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.5.0"
+   "version": "3.4.3"
   }
  },
  "nbformat": 4,