fixed problems, new pull

arrays_strings/unique_chars/unique_chars_challenge.ipynb

@@ -34,7 +34,6 @@
    "source": [
     "## Constraints\n",
     "\n",
-
     "* Can you assume the string is ASCII?\n",
     "    * Yes\n",
     "    * Note: Unicode strings could require special handling depending on your language\n",
@@ -73,15 +72,22 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
     "collapsed": false
    },
    "outputs": [],
    "source": [
     "def unique_chars(string):\n",
-    "    # TODO: Implement me\n",
-    "    pass"
+    "    from collections import defaultdict\n",
+    "    \n",
+    "    char_table = defaultdict(int)\n",
+    "    for c in string:\n",
+    "        if char_table[c] > 0:\n",
+    "            return False\n",
+    "        else:\n",
+    "            char_table[c] = 1\n",
+    "    return True"
    ]
   },
   {
@@ -100,11 +106,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {
     "collapsed": false
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Success: test_unique_chars\n"
+     ]
+    }
+   ],
    "source": [
     "# %load test_unique_chars.py\n",
     "from nose.tools import assert_equal\n",
@@ -159,7 +173,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython2",
-   "version": "2.7.10"
+   "version": "2.7.6"
   }
  },
  "nbformat": 4,