Added info about the pythonic code not being in-place.

arrays-strings/reverse_string.ipynb

@@ -10,7 +10,7 @@
     "* [Test Cases](#Test-Cases)\n",
     "* [Algorithm](#Algorithm)\n",
     "* [Code](#Code)\n",
-    "* [Pythonic-Code](#Pythonic-Code)"
+    "* [Pythonic-Code: Not In-Place](#Pythonic-Code:-Not-In-Place)"
    ]
   },
   {
@@ -22,7 +22,7 @@
     "* Based on the function signature, it seems you have to implement this in C/C++?\n",
     "    * Yes\n",
     "* Can you use additional data structures?\n",
-    "    * No"
+    "    * No, do the operation in-place"
    ]
   },
   {
@@ -117,7 +117,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Pythonic Code\n",
+    "## Pythonic-Code: Not In-Place\n",
     "\n",
     "The following code is Pythonic, but requires using additional data structures as Python strings are immutable.  You could use a bytearray or a list instead of a string to simulate manipulating an array of characters."
    ]