diff --git a/online_judges/mult_other_numbers/__init__.py b/online_judges/mult_other_numbers/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/online_judges/mult_other_numbers/mult_other_numbers_challenge.ipynb b/online_judges/mult_other_numbers/mult_other_numbers_challenge.ipynb
new file mode 100644
index 0000000..020b44c
--- /dev/null
+++ b/online_judges/mult_other_numbers/mult_other_numbers_challenge.ipynb
@@ -0,0 +1,172 @@
+{
+ "cells": [
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "# Challenge Notebook"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Problem: Given a list of ints, find the products of every other int for each index.\n",
+ "\n",
+ "* [Constraints](#Constraints)\n",
+ "* [Test Cases](#Test-Cases)\n",
+ "* [Algorithm](#Algorithm)\n",
+ "* [Code](#Code)\n",
+ "* [Unit Test](#Unit-Test)\n",
+ "* [Solution Notebook](#Solution-Notebook)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Constraints\n",
+ "\n",
+ "* Can we use division?\n",
+ " * No\n",
+ "* Is the output a list of ints?\n",
+ " * Yes\n",
+ "* Can we assume the inputs are valid?\n",
+ " * No\n",
+ "* Can we assume this fits memory?\n",
+ " * Yes"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Test Cases\n",
+ "\n",
+ "\n",
+ "* None -> TypeError\n",
+ "* [] -> []\n",
+ "* [0] -> []\n",
+ "* [0, 1] -> [1, 0]\n",
+ "* [0, 1, 2] -> [2, 0, 0]\n",
+ "* [1, 2, 3, 4] -> [24, 12, 8, 6]\n",
+ "
"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Algorithm\n",
+ "\n",
+ "Refer to the [Solution Notebook](). If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Code"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [],
+ "source": [
+ "class Solution(object):\n",
+ "\n",
+ " def mult_other_numbers(self, array):\n",
+ " # TODO: Implement me\n",
+ " pass"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Unit Test"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "**The following unit test is expected to fail until you solve the challenge.**"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [],
+ "source": [
+ "# %load test_mult_other_numbers.py\n",
+ "from nose.tools import assert_equal, assert_raises\n",
+ "\n",
+ "\n",
+ "class TestMultOtherNumbers(object):\n",
+ "\n",
+ " def test_mult_other_numbers(self):\n",
+ " solution = Solution()\n",
+ " assert_raises(TypeError, solution.mult_other_numbers, None)\n",
+ " assert_equal(solution.mult_other_numbers([0]), [])\n",
+ " assert_equal(solution.mult_other_numbers([0, 1]), [1, 0])\n",
+ " assert_equal(solution.mult_other_numbers([0, 1, 2]), [2, 0, 0])\n",
+ " assert_equal(solution.mult_other_numbers([1, 2, 3, 4]), [24, 12, 8, 6])\n",
+ " print('Success: test_mult_other_numbers')\n",
+ "\n",
+ "\n",
+ "def main():\n",
+ " test = TestMultOtherNumbers()\n",
+ " test.test_mult_other_numbers()\n",
+ "\n",
+ "\n",
+ "if __name__ == '__main__':\n",
+ " main()"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Solution Notebook\n",
+ "\n",
+ "Review the [Solution Notebook]() for a discussion on algorithms and code solutions."
+ ]
+ }
+ ],
+ "metadata": {
+ "kernelspec": {
+ "display_name": "Python 3",
+ "language": "python",
+ "name": "python3"
+ },
+ "language_info": {
+ "codemirror_mode": {
+ "name": "ipython",
+ "version": 3
+ },
+ "file_extension": ".py",
+ "mimetype": "text/x-python",
+ "name": "python",
+ "nbconvert_exporter": "python",
+ "pygments_lexer": "ipython3",
+ "version": "3.5.0"
+ }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}
diff --git a/online_judges/mult_other_numbers/mult_other_numbers_solution.ipynb b/online_judges/mult_other_numbers/mult_other_numbers_solution.ipynb
new file mode 100644
index 0000000..74d857c
--- /dev/null
+++ b/online_judges/mult_other_numbers/mult_other_numbers_solution.ipynb
@@ -0,0 +1,265 @@
+{
+ "cells": [
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "# Solution Notebook"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Problem: Given a list of ints, find the products of every other int for each index.\n",
+ "\n",
+ "* [Constraints](#Constraints)\n",
+ "* [Test Cases](#Test-Cases)\n",
+ "* [Algorithm](#Algorithm)\n",
+ "* [Code](#Code)\n",
+ "* [Unit Test](#Unit-Test)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Constraints\n",
+ "\n",
+ "* Can we use division?\n",
+ " * No\n",
+ "* Is the output a list of ints?\n",
+ " * Yes\n",
+ "* Can we assume the inputs are valid?\n",
+ " * No\n",
+ "* Can we assume this fits memory?\n",
+ " * Yes"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Test Cases\n",
+ "\n",
+ "\n",
+ "* None -> TypeError\n",
+ "* [] -> []\n",
+ "* [0] -> []\n",
+ "* [0, 1] -> [1, 0]\n",
+ "* [0, 1, 2] -> [2, 0, 0]\n",
+ "* [1, 2, 3, 4] -> [24, 12, 8, 6]\n",
+ "
"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Algorithm\n",
+ "\n",
+ "### Brute force:\n",
+ "\n",
+ "\n",
+ "sum = 1\n",
+ " |\n",
+ "[1, 2, 3, 4]\n",
+ " ^\n",
+ "skip if both pointers are pointing to the same spot\n",
+ " |\n",
+ "[1, 2, 3, 4]\n",
+ " ^\n",
+ "sum *= 2\n",
+ " |\n",
+ "[1, 2, 3, 4]\n",
+ " ^\n",
+ "sum *= 3\n",
+ " |\n",
+ "[1, 2, 3, 4]\n",
+ " ^\n",
+ "sum *= 4\n",
+ "results.append(sum)\n",
+ "results = [24]\n",
+ "\n",
+ "repeat for every element in the input list to obtain:\n",
+ "\n",
+ "[24, 12, 8, 6]\n",
+ " \n",
+ "
\n",
+ "\n",
+ "Complexity:\n",
+ "* Time: O(n^2)\n",
+ "* Space: O(n)\n",
+ "\n",
+ "### Greedy\n",
+ "\n",
+ "\n",
+ "input = [1, 2, 3, 4]\n",
+ "result = [2*3*4, 1*3*4, 1*2*4, 1*2*3]\n",
+ "\n",
+ "Note we are duplicating multiplications with the brute force approach.\n",
+ "\n",
+ "We'll calculate all products before an index, and all products after an index.\n",
+ "We'll then multiple these two together to form the result.\n",
+ "\n",
+ "input = [1, 2, 3, 4]\n",
+ "before = [1, 1, 1*2, 1*2*3]\n",
+ "after = [2*3*4, 1*3*4, 1*2*4, 1]\n",
+ "result = [ 24, 12, 8, 6] \n",
+ "
\n",
+ "\n",
+ "Complexity:\n",
+ "* Time: O(n)\n",
+ "* Space: O(n)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Code"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 1,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [],
+ "source": [
+ "class Solution(object):\n",
+ "\n",
+ " def mult_other_numbers_brute(self, array):\n",
+ " if array is None:\n",
+ " raise TypeError('array cannot be None')\n",
+ " if not array:\n",
+ " return array\n",
+ " if len(array) == 1:\n",
+ " return []\n",
+ " result = []\n",
+ " for i in range(len(array)):\n",
+ " curr_sum = 1\n",
+ " for j in range(len(array)):\n",
+ " if i == j:\n",
+ " continue\n",
+ " curr_sum *= array[j]\n",
+ " result.append(curr_sum)\n",
+ " return result\n",
+ "\n",
+ " def mult_other_numbers(self, array):\n",
+ " if array is None:\n",
+ " raise TypeError('array cannot be None')\n",
+ " if not array:\n",
+ " return array\n",
+ " if len(array) == 1:\n",
+ " return []\n",
+ " result = [None] * len(array)\n",
+ " curr_product = 1\n",
+ " for i in range(len(array)):\n",
+ " result[i] = curr_product\n",
+ " curr_product *= array[i]\n",
+ " curr_product = 1\n",
+ " for i in range(len(array))[::-1]:\n",
+ " result[i] *= curr_product\n",
+ " curr_product *= array[i]\n",
+ " return result"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Unit Test"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 2,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Overwriting test_mult_other_numbers.py\n"
+ ]
+ }
+ ],
+ "source": [
+ "%%writefile test_mult_other_numbers.py\n",
+ "from nose.tools import assert_equal, assert_raises\n",
+ "\n",
+ "\n",
+ "class TestMultOtherNumbers(object):\n",
+ "\n",
+ " def test_mult_other_numbers(self):\n",
+ " solution = Solution()\n",
+ " assert_raises(TypeError, solution.mult_other_numbers, None)\n",
+ " assert_equal(solution.mult_other_numbers([0]), [])\n",
+ " assert_equal(solution.mult_other_numbers([0, 1]), [1, 0])\n",
+ " assert_equal(solution.mult_other_numbers([0, 1, 2]), [2, 0, 0])\n",
+ " assert_equal(solution.mult_other_numbers([1, 2, 3, 4]), [24, 12, 8, 6])\n",
+ " print('Success: test_mult_other_numbers')\n",
+ "\n",
+ "\n",
+ "def main():\n",
+ " test = TestMultOtherNumbers()\n",
+ " test.test_mult_other_numbers()\n",
+ "\n",
+ "\n",
+ "if __name__ == '__main__':\n",
+ " main()"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 3,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "Success: test_mult_other_numbers\n"
+ ]
+ }
+ ],
+ "source": [
+ "%run -i test_mult_other_numbers.py"
+ ]
+ }
+ ],
+ "metadata": {
+ "kernelspec": {
+ "display_name": "Python 3",
+ "language": "python",
+ "name": "python3"
+ },
+ "language_info": {
+ "codemirror_mode": {
+ "name": "ipython",
+ "version": 3
+ },
+ "file_extension": ".py",
+ "mimetype": "text/x-python",
+ "name": "python",
+ "nbconvert_exporter": "python",
+ "pygments_lexer": "ipython3",
+ "version": "3.5.0"
+ }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}
diff --git a/online_judges/mult_other_numbers/test_mult_other_numbers.py b/online_judges/mult_other_numbers/test_mult_other_numbers.py
new file mode 100644
index 0000000..c1c5cca
--- /dev/null
+++ b/online_judges/mult_other_numbers/test_mult_other_numbers.py
@@ -0,0 +1,22 @@
+from nose.tools import assert_equal, assert_raises
+
+
+class TestMultOtherNumbers(object):
+
+ def test_mult_other_numbers(self):
+ solution = Solution()
+ assert_raises(TypeError, solution.mult_other_numbers, None)
+ assert_equal(solution.mult_other_numbers([0]), [])
+ assert_equal(solution.mult_other_numbers([0, 1]), [1, 0])
+ assert_equal(solution.mult_other_numbers([0, 1, 2]), [2, 0, 0])
+ assert_equal(solution.mult_other_numbers([1, 2, 3, 4]), [24, 12, 8, 6])
+ print('Success: test_mult_other_numbers')
+
+
+def main():
+ test = TestMultOtherNumbers()
+ test.test_mult_other_numbers()
+
+
+if __name__ == '__main__':
+ main()
\ No newline at end of file