diff --git a/arrays_strings/str_diff/str_diff_challenge.ipynb b/arrays_strings/str_diff/str_diff_challenge.ipynb
index aeb36f9..323fdb4 100644
--- a/arrays_strings/str_diff/str_diff_challenge.ipynb
+++ b/arrays_strings/str_diff/str_diff_challenge.ipynb
@@ -34,6 +34,7 @@
    "source": [
     "## Constraints\n",
     "\n",
+    "* Assume two strings str1, str2, where str2 contains the same set of characters in str1 with one additional character.\n",
     "* Can we assume the strings are ASCII?\n",
     "    * Yes\n",
     "* Is case important?\n",
diff --git a/arrays_strings/str_diff/str_diff_solution.ipynb b/arrays_strings/str_diff/str_diff_solution.ipynb
index 90813c4..23b1471 100644
--- a/arrays_strings/str_diff/str_diff_solution.ipynb
+++ b/arrays_strings/str_diff/str_diff_solution.ipynb
@@ -76,7 +76,7 @@
     "\n",
     "Complexity:\n",
     "* Time: O(m+n), where m and n are the lengths of s, t\n",
-    "* Space: O(1), for the dict, where h is the unique chars in s"
+    "* Space: O(1)"
    ]
   },
   {