diff --git a/bit_manipulation/draw_line/__init__.py b/bit_manipulation/draw_line/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/bit_manipulation/draw_line/draw_line_challenge.ipynb b/bit_manipulation/draw_line/draw_line_challenge.ipynb
new file mode 100644
index 0000000..ed9ce5d
--- /dev/null
+++ b/bit_manipulation/draw_line/draw_line_challenge.ipynb
@@ -0,0 +1,180 @@
+{
+ "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: Implement the method draw_line(screen, width, x1, x2) where screen is a list of bytes, width is divisible by 8, and x1, x2 are absolute pixel positions.\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 assume the inputs are valid?\n",
+ " * No\n",
+ "* For the output, do we set corresponding bits in screen?\n",
+ " * Yes\n",
+ "* Can we assume this fits memory?\n",
+ " * Yes"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Test Cases\n",
+ "\n",
+ "* Invalid inputs -> Exception\n",
+ " * screen is empty\n",
+ " * width = 0\n",
+ " * any input param is None\n",
+ " * x1 or x2 is out of bounds\n",
+ "* General case for len(screen) = 20, width = 32:\n",
+ " * x1 = 2, x2 = 6\n",
+ " * screen[0] = int('00111110', base=2)\n",
+ " * x1 = 68, x2 = 80\n",
+ " * screen[8], int('00001111', base=2)\n",
+ " * screen[9], int('11111111', base=2)\n",
+ " * screen[10], int('10000000', base=2)"
+ ]
+ },
+ {
+ "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 BitsScreen(object):\n",
+ "\n",
+ " def draw_line(self, screen, width, x1, x2):\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_draw_line.py\n",
+ "from nose.tools import assert_equal\n",
+ "\n",
+ "\n",
+ "class TestBitsScreen(object):\n",
+ "\n",
+ " def test_draw_line(self):\n",
+ " bits_screen = BitsScreen()\n",
+ " screen = []\n",
+ " for _ in range(20):\n",
+ " screen.append(int('00000000', base=2))\n",
+ " bits_screen.draw_line(screen, width=32, x1=68, x2=80)\n",
+ " assert_equal(screen[8], int('00001111', base=2))\n",
+ " assert_equal(screen[9], int('11111111', base=2))\n",
+ " assert_equal(screen[10], int('10000000', base=2))\n",
+ " bits_screen.draw_line(screen, width=32, x1=2, x2=6)\n",
+ " assert_equal(screen[0], int('00111110', base=2))\n",
+ " bits_screen.draw_line(screen, width=32, x1=10, x2=13)\n",
+ " assert_equal(screen[1], int('00111100', base=2))\n",
+ " print('Success: test_draw_line')\n",
+ "\n",
+ "\n",
+ "def main():\n",
+ " test = TestBitsScreen()\n",
+ " test.test_draw_line()\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/bit_manipulation/draw_line/draw_line_solution.ipynb b/bit_manipulation/draw_line/draw_line_solution.ipynb
new file mode 100644
index 0000000..798f46f
--- /dev/null
+++ b/bit_manipulation/draw_line/draw_line_solution.ipynb
@@ -0,0 +1,288 @@
+{
+ "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: Implement the method draw_line(screen, width, x1, x2) where screen is a list of bytes, width is divisible by 8, and x1, x2 are absolute pixel positions.\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 assume the inputs are valid?\n",
+ " * No\n",
+ "* For the output, do we set corresponding bits in screen?\n",
+ " * Yes\n",
+ "* Can we assume this fits memory?\n",
+ " * Yes"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Test Cases\n",
+ "\n",
+ "* Invalid inputs -> Exception\n",
+ " * screen is empty\n",
+ " * width = 0\n",
+ " * any input param is None\n",
+ " * x1 or x2 is out of bounds\n",
+ "* General case for len(screen) = 20, width = 32:\n",
+ " * x1 = 2, x2 = 6\n",
+ " * screen[0] = int('00111110', base=2)\n",
+ " * x1 = 68, x2 = 80\n",
+ " * screen[8], int('00001111', base=2)\n",
+ " * screen[9], int('11111111', base=2)\n",
+ " * screen[10], int('10000000', base=2)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Algorithm\n",
+ "\n",
+ "* Set start offset to x1 % 8\n",
+ "* Set end offset to x2 % 8\n",
+ "* Determine where the first and last full bytes are\n",
+ " * First full byte = x1 // 8\n",
+ " * Increment by 1 if start offset != 0\n",
+ " * Last full byte = x2 // 8\n",
+ " * Decrement by 1 if end offset != 7\n",
+ " * Fill the bytes with 1111 1111\n",
+ "* If x1 and x2 are in the same byte\n",
+ "\n",
+ "\n",
+ " x1 = 2\n",
+ " x2 = 6\n",
+ "\n",
+ " index 0123 4567\n",
+ " byte 0011 1110\n",
+ "\n",
+ " We want to build left and right masks such that:\n",
+ "\n",
+ " left 0011 1111\n",
+ " right 1111 1110\n",
+ " ----------------\n",
+ " 0011 1110 left & right\n",
+ "\n",
+ " Build the left mask:\n",
+ "\n",
+ " left 0000 0001 1\n",
+ " 0100 0000 1 << (8 - x1)\n",
+ " 0011 1111 (1 << (8 - x1)) - 1\n",
+ "\n",
+ " Build the right mask:\n",
+ "\n",
+ " right 0000 0000 1\n",
+ " 0000 0010 1 << (8 - x2 - 1)\n",
+ " 0000 0001 (1 << (8 - x2 - 1) - 1\n",
+ " 1111 1110 ~((1 << (8 - x2 - 1) - 1)\n",
+ "\n",
+ " Combine the left and right masks:\n",
+ "\n",
+ " left 0011 1111\n",
+ " right 1111 1110\n",
+ " ----------------\n",
+ " 0011 1110 left & right\n",
+ "\n",
+ " Set screen[x1//8] or screen[x2//8] |= mask\n",
+ "
\n",
+ "* Else\n",
+ "\n",
+ " If our starting partial byte is:\n",
+ " 0000 1111\n",
+ "\n",
+ " Build start mask:\n",
+ " \n",
+ " start 0000 0001 1\n",
+ " 0001 0000 1 << 1 << start offset\n",
+ " 0000 1111 (1 << 1 << start offset) - 1\n",
+ "\n",
+ " If our ending partial byte is:\n",
+ " 1111 1100\n",
+ "\n",
+ " Build end mask:\n",
+ " \n",
+ " end 1000 0000 0x10000000\n",
+ " 1111 1100 0x10000000 >> end offset\n",
+ "\n",
+ " Set screen[x1//8] |= start mask\n",
+ " Set screen[x2//8] |= end mask\n",
+ "
\n",
+ "\n",
+ "Complexity:\n",
+ "* Time: O(length of screen)\n",
+ "* Space: O(1)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "metadata": {},
+ "source": [
+ "## Code"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 1,
+ "metadata": {
+ "collapsed": false
+ },
+ "outputs": [],
+ "source": [
+ "class BitsScreen(object):\n",
+ "\n",
+ " def draw_line(self, screen, width, x1, x2):\n",
+ " if None in (screen, width, x1, x2):\n",
+ " raise TypeError('Invalid argument: None')\n",
+ " if not screen or not width:\n",
+ " raise ValueError('Invalid arg: Empty screen or width')\n",
+ " MAX_BIT_VALUE = len(screen) * 8\n",
+ " if x1 < 0 or x2 < 0 or x1 >= MAX_BIT_VALUE or x2 >= MAX_BIT_VALUE:\n",
+ " raise ValueError('Invalid arg: x1 or x2 out of bounds')\n",
+ " start_bit = x1 % 8\n",
+ " end_bit = x2 % 8\n",
+ " first_full_byte = x1 // 8\n",
+ " if start_bit != 0:\n",
+ " first_full_byte += 1\n",
+ " last_full_byte = x2 // 8\n",
+ " if end_bit != (8 - 1):\n",
+ " last_full_byte -= 1\n",
+ " for byte in range(first_full_byte, last_full_byte + 1):\n",
+ " screen[byte] = int('11111111', base=2)\n",
+ " start_byte = x1 // 8\n",
+ " end_byte = x2 // 8\n",
+ " if start_byte == end_byte:\n",
+ " left_mask = (1 << (8 - start_bit)) - 1\n",
+ " right_mask = ~((1 << (8 - end_bit - 1)) - 1)\n",
+ " mask = left_mask & right_mask\n",
+ " screen[start_byte] |= mask\n",
+ " else:\n",
+ " start_mask = (1 << (8 - start_bit)) - 1\n",
+ " end_mask = 1 << (8 - end_bit - 1)\n",
+ " screen[start_byte] |= start_mask\n",
+ " screen[end_byte] |= end_mask"
+ ]
+ },
+ {
+ "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_draw_line.py\n"
+ ]
+ }
+ ],
+ "source": [
+ "%%writefile test_draw_line.py\n",
+ "from nose.tools import assert_equal\n",
+ "\n",
+ "\n",
+ "class TestBitsScreen(object):\n",
+ "\n",
+ " def test_draw_line(self):\n",
+ " bits_screen = BitsScreen()\n",
+ " screen = []\n",
+ " for _ in range(20):\n",
+ " screen.append(int('00000000', base=2))\n",
+ " bits_screen.draw_line(screen, width=32, x1=68, x2=80)\n",
+ " assert_equal(screen[8], int('00001111', base=2))\n",
+ " assert_equal(screen[9], int('11111111', base=2))\n",
+ " assert_equal(screen[10], int('10000000', base=2))\n",
+ " bits_screen.draw_line(screen, width=32, x1=2, x2=6)\n",
+ " assert_equal(screen[0], int('00111110', base=2))\n",
+ " bits_screen.draw_line(screen, width=32, x1=10, x2=13)\n",
+ " assert_equal(screen[1], int('00111100', base=2))\n",
+ " print('Success: test_draw_line')\n",
+ "\n",
+ "\n",
+ "def main():\n",
+ " test = TestBitsScreen()\n",
+ " test.test_draw_line()\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_draw_line\n"
+ ]
+ }
+ ],
+ "source": [
+ "%run -i test_draw_line.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": "3.4.3"
+ }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}
diff --git a/bit_manipulation/draw_line/test_draw_line.py b/bit_manipulation/draw_line/test_draw_line.py
new file mode 100644
index 0000000..69f736d
--- /dev/null
+++ b/bit_manipulation/draw_line/test_draw_line.py
@@ -0,0 +1,28 @@
+from nose.tools import assert_equal
+
+
+class TestBitsScreen(object):
+
+ def test_draw_line(self):
+ bits_screen = BitsScreen()
+ screen = []
+ for _ in range(20):
+ screen.append(int('00000000', base=2))
+ bits_screen.draw_line(screen, width=32, x1=68, x2=80)
+ assert_equal(screen[8], int('00001111', base=2))
+ assert_equal(screen[9], int('11111111', base=2))
+ assert_equal(screen[10], int('10000000', base=2))
+ bits_screen.draw_line(screen, width=32, x1=2, x2=6)
+ assert_equal(screen[0], int('00111110', base=2))
+ bits_screen.draw_line(screen, width=32, x1=10, x2=13)
+ assert_equal(screen[1], int('00111100', base=2))
+ print('Success: test_draw_line')
+
+
+def main():
+ test = TestBitsScreen()
+ test.test_draw_line()
+
+
+if __name__ == '__main__':
+ main()
\ No newline at end of file