diff --git a/arrays_strings/permutation/permutation_challenge.ipynb b/arrays_strings/permutation/permutation_challenge.ipynb
index 4125371..221b026 100644
--- a/arrays_strings/permutation/permutation_challenge.ipynb
+++ b/arrays_strings/permutation/permutation_challenge.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Determine if a string is a permutation of another string\n",
+    "## Problem: Determine if a string is a permutation of another string.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/arrays_strings/permutation/permutation_solution.ipynb b/arrays_strings/permutation/permutation_solution.ipynb
index b36f333..1ec421c 100644
--- a/arrays_strings/permutation/permutation_solution.ipynb
+++ b/arrays_strings/permutation/permutation_solution.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Determine if a string is a permutation of another string\n",
+    "## Problem: Determine if a string is a permutation of another string.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/arrays_strings/rotation/rotation_challenge.ipynb b/arrays_strings/rotation/rotation_challenge.ipynb
index 6fd765d..adf55d3 100644
--- a/arrays_strings/rotation/rotation_challenge.ipynb
+++ b/arrays_strings/rotation/rotation_challenge.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Determine if a string s1 is a rotation of another string s2, by calling (only once) a function is_substring\n",
+    "## Problem: Determine if a string s1 is a rotation of another string s2, by calling (only once) a function is_substring.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/arrays_strings/rotation/rotation_solution.ipynb b/arrays_strings/rotation/rotation_solution.ipynb
index a153a02..4f64402 100644
--- a/arrays_strings/rotation/rotation_solution.ipynb
+++ b/arrays_strings/rotation/rotation_solution.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Determine if a string s1 is a rotation of another string s2, by calling (only once) a function is_substring\n",
+    "## Problem: Determine if a string s1 is a rotation of another string s2, by calling (only once) a function is_substring.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/arrays_strings/unique_chars/unique_chars_challenge.ipynb b/arrays_strings/unique_chars/unique_chars_challenge.ipynb
index 535a5eb..2daf719 100644
--- a/arrays_strings/unique_chars/unique_chars_challenge.ipynb
+++ b/arrays_strings/unique_chars/unique_chars_challenge.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Implement an algorithm to determine if a string has all unique characters\n",
+    "## Problem: Implement an algorithm to determine if a string has all unique characters.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/arrays_strings/unique_chars/unique_chars_solution.ipynb b/arrays_strings/unique_chars/unique_chars_solution.ipynb
index 971274b..b5b5ce3 100644
--- a/arrays_strings/unique_chars/unique_chars_solution.ipynb
+++ b/arrays_strings/unique_chars/unique_chars_solution.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Implement an algorithm to determine if a string has all unique characters\n",
+    "## Problem: Implement an algorithm to determine if a string has all unique characters.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/linked_lists/kth_to_last_elem/kth_to_last_elem_challenge.ipynb b/linked_lists/kth_to_last_elem/kth_to_last_elem_challenge.ipynb
index e690c57..eaaddce 100644
--- a/linked_lists/kth_to_last_elem/kth_to_last_elem_challenge.ipynb
+++ b/linked_lists/kth_to_last_elem/kth_to_last_elem_challenge.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Find the kth to last element of a linked list\n",
+    "## Problem: Find the kth to last element of a linked list.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/linked_lists/kth_to_last_elem/kth_to_last_elem_solution.ipynb b/linked_lists/kth_to_last_elem/kth_to_last_elem_solution.ipynb
index e1533b3..f2acd01 100644
--- a/linked_lists/kth_to_last_elem/kth_to_last_elem_solution.ipynb
+++ b/linked_lists/kth_to_last_elem/kth_to_last_elem_solution.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Find the kth to last element of a linked list\n",
+    "## Problem: Find the kth to last element of a linked list.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/linked_lists/linked_list/linked_list_challenge.ipynb b/linked_lists/linked_list/linked_list_challenge.ipynb
index 80dec08..5ebf576 100644
--- a/linked_lists/linked_list/linked_list_challenge.ipynb
+++ b/linked_lists/linked_list/linked_list_challenge.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Implement a linked list with insert, append, find, delete, length, and print methods\n",
+    "## Problem: Implement a linked list with insert, append, find, delete, length, and print methods.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/linked_lists/linked_list/linked_list_solution.ipynb b/linked_lists/linked_list/linked_list_solution.ipynb
index cebf074..104375b 100644
--- a/linked_lists/linked_list/linked_list_solution.ipynb
+++ b/linked_lists/linked_list/linked_list_solution.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Implement a linked list with insert, append, find, delete, length, and print methods\n",
+    "## Problem: Implement a linked list with insert, append, find, delete, length, and print methods.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/linked_lists/remove_duplicates/remove_duplicates_challenge.ipynb b/linked_lists/remove_duplicates/remove_duplicates_challenge.ipynb
index d9bff27..f9b6ab7 100644
--- a/linked_lists/remove_duplicates/remove_duplicates_challenge.ipynb
+++ b/linked_lists/remove_duplicates/remove_duplicates_challenge.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Remove duplicates from a linked list\n",
+    "## Problem: Remove duplicates from a linked list.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/linked_lists/remove_duplicates/remove_duplicates_solution.ipynb b/linked_lists/remove_duplicates/remove_duplicates_solution.ipynb
index 77f598b..f533f9b 100644
--- a/linked_lists/remove_duplicates/remove_duplicates_solution.ipynb
+++ b/linked_lists/remove_duplicates/remove_duplicates_solution.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Remove duplicates from a linked list\n",
+    "## Problem: Remove duplicates from a linked list.\n",
     "\n",
     "* [Constraints](#Constraints)\n",
     "* [Test Cases](#Test-Cases)\n",
diff --git a/recursion_dynamic/coin_change_ways/coin_change_ways_challenge.ipynb b/recursion_dynamic/coin_change_ways/coin_change_ways_challenge.ipynb
index af60a76..8d62bdf 100644
--- a/recursion_dynamic/coin_change_ways/coin_change_ways_challenge.ipynb
+++ b/recursion_dynamic/coin_change_ways/coin_change_ways_challenge.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Counting Ways of Making Change\n",
+    "## Problem: Counting Ways of Making Change.\n",
     "\n",
     "* [Explanation](#Explanation)\n",
     "* [Test Cases](#Test-Cases)\n",
@@ -137,21 +137,21 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 2",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "python2"
+   "name": "python3"
   },
   "language_info": {
    "codemirror_mode": {
     "name": "ipython",
-    "version": 2
+    "version": 3
    },
    "file_extension": ".py",
    "mimetype": "text/x-python",
    "name": "python",
    "nbconvert_exporter": "python",
-   "pygments_lexer": "ipython2",
-   "version": "2.7.10"
+   "pygments_lexer": "ipython3",
+   "version": "3.5.0"
   }
  },
  "nbformat": 4,
diff --git a/recursion_dynamic/coin_change_ways/coin_change_ways_solution.ipynb b/recursion_dynamic/coin_change_ways/coin_change_ways_solution.ipynb
index caefe1b..72bffcf 100644
--- a/recursion_dynamic/coin_change_ways/coin_change_ways_solution.ipynb
+++ b/recursion_dynamic/coin_change_ways/coin_change_ways_solution.ipynb
@@ -18,7 +18,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Counting Ways of Making Change\n",
+    "## Problem: Counting Ways of Making Change.\n",
     "\n",
     "* [Hints](#Hints)\n",
     "* [Algorithm](#Algorithm)\n",
@@ -150,21 +150,21 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 2",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "python2"
+   "name": "python3"
   },
   "language_info": {
    "codemirror_mode": {
     "name": "ipython",
-    "version": 2
+    "version": 3
    },
    "file_extension": ".py",
    "mimetype": "text/x-python",
    "name": "python",
    "nbconvert_exporter": "python",
-   "pygments_lexer": "ipython2",
-   "version": "2.7.10"
+   "pygments_lexer": "ipython3",
+   "version": "3.5.0"
   }
  },
  "nbformat": 4,