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Add draw line challenge
This commit is contained in:
Donne Martin
parent
c06594871d
commit
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0
bit_manipulation/draw_line/__init__.py
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0
bit_manipulation/draw_line/__init__.py
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180
bit_manipulation/draw_line/draw_line_challenge.ipynb
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180
bit_manipulation/draw_line/draw_line_challenge.ipynb
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"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)."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Challenge Notebook"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 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",
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"\n",
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"* [Constraints](#Constraints)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)\n",
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"* [Solution Notebook](#Solution-Notebook)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints\n",
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"\n",
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"* Can we assume the inputs are valid?\n",
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" * No\n",
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"* For the output, do we set corresponding bits in screen?\n",
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" * Yes\n",
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"* Can we assume this fits memory?\n",
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" * Yes"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"* Invalid inputs -> Exception\n",
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" * screen is empty\n",
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" * width = 0\n",
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" * any input param is None\n",
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" * x1 or x2 is out of bounds\n",
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"* General case for len(screen) = 20, width = 32:\n",
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" * x1 = 2, x2 = 6\n",
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" * screen[0] = int('00111110', base=2)\n",
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" * x1 = 68, x2 = 80\n",
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" * screen[8], int('00001111', base=2)\n",
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" * screen[9], int('11111111', base=2)\n",
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" * screen[10], int('10000000', base=2)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"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."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"class BitsScreen(object):\n",
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"\n",
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" def draw_line(self, screen, width, x1, x2):\n",
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" # TODO: Implement me\n",
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" pass"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Unit Test"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"**The following unit test is expected to fail until you solve the challenge.**"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# %load test_draw_line.py\n",
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"from nose.tools import assert_equal\n",
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"\n",
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"\n",
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"class TestBitsScreen(object):\n",
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"\n",
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" def test_draw_line(self):\n",
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" bits_screen = BitsScreen()\n",
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" screen = []\n",
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" for _ in range(20):\n",
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" screen.append(int('00000000', base=2))\n",
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" bits_screen.draw_line(screen, width=32, x1=68, x2=80)\n",
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" assert_equal(screen[8], int('00001111', base=2))\n",
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" assert_equal(screen[9], int('11111111', base=2))\n",
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" assert_equal(screen[10], int('10000000', base=2))\n",
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" bits_screen.draw_line(screen, width=32, x1=2, x2=6)\n",
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" assert_equal(screen[0], int('00111110', base=2))\n",
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" bits_screen.draw_line(screen, width=32, x1=10, x2=13)\n",
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" assert_equal(screen[1], int('00111100', base=2))\n",
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" print('Success: test_draw_line')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestBitsScreen()\n",
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" test.test_draw_line()\n",
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"\n",
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"\n",
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"if __name__ == '__main__':\n",
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" main()"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Solution Notebook\n",
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"\n",
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"Review the [Solution Notebook]() for a discussion on algorithms and code solutions."
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.5.0"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 0
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}
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288
bit_manipulation/draw_line/draw_line_solution.ipynb
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bit_manipulation/draw_line/draw_line_solution.ipynb
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@ -0,0 +1,288 @@
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{
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||||
"cells": [
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{
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||||
"cell_type": "markdown",
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||||
"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)."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Solution Notebook"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## 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",
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"\n",
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"* [Constraints](#Constraints)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints\n",
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"\n",
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"* Can we assume the inputs are valid?\n",
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" * No\n",
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"* For the output, do we set corresponding bits in screen?\n",
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" * Yes\n",
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"* Can we assume this fits memory?\n",
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" * Yes"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"* Invalid inputs -> Exception\n",
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" * screen is empty\n",
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" * width = 0\n",
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" * any input param is None\n",
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" * x1 or x2 is out of bounds\n",
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"* General case for len(screen) = 20, width = 32:\n",
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" * x1 = 2, x2 = 6\n",
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" * screen[0] = int('00111110', base=2)\n",
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" * x1 = 68, x2 = 80\n",
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" * screen[8], int('00001111', base=2)\n",
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" * screen[9], int('11111111', base=2)\n",
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" * screen[10], int('10000000', base=2)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"* Set start offset to x1 % 8\n",
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"* Set end offset to x2 % 8\n",
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"* Determine where the first and last full bytes are\n",
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" * First full byte = x1 // 8\n",
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" * Increment by 1 if start offset != 0\n",
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" * Last full byte = x2 // 8\n",
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" * Decrement by 1 if end offset != 7\n",
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" * Fill the bytes with 1111 1111\n",
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"* If x1 and x2 are in the same byte\n",
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"\n",
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"<pre>\n",
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" x1 = 2\n",
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" x2 = 6\n",
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"\n",
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" index 0123 4567\n",
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" byte 0011 1110\n",
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"\n",
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" We want to build left and right masks such that:\n",
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"\n",
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" left 0011 1111\n",
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" right 1111 1110\n",
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" ----------------\n",
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" 0011 1110 left & right\n",
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"\n",
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" Build the left mask:\n",
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"\n",
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" left 0000 0001 1\n",
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" 0100 0000 1 << (8 - x1)\n",
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" 0011 1111 (1 << (8 - x1)) - 1\n",
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"\n",
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" Build the right mask:\n",
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"\n",
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" right 0000 0000 1\n",
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" 0000 0010 1 << (8 - x2 - 1)\n",
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" 0000 0001 (1 << (8 - x2 - 1) - 1\n",
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" 1111 1110 ~((1 << (8 - x2 - 1) - 1)\n",
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"\n",
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" Combine the left and right masks:\n",
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"\n",
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" left 0011 1111\n",
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" right 1111 1110\n",
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" ----------------\n",
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" 0011 1110 left & right\n",
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"\n",
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" Set screen[x1//8] or screen[x2//8] |= mask\n",
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"</pre>\n",
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"* Else\n",
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"<pre>\n",
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" If our starting partial byte is:\n",
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" 0000 1111\n",
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"\n",
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" Build start mask:\n",
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" \n",
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" start 0000 0001 1\n",
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" 0001 0000 1 << 1 << start offset\n",
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" 0000 1111 (1 << 1 << start offset) - 1\n",
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"\n",
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" If our ending partial byte is:\n",
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" 1111 1100\n",
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"\n",
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" Build end mask:\n",
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" \n",
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" end 1000 0000 0x10000000\n",
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" 1111 1100 0x10000000 >> end offset\n",
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"\n",
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" Set screen[x1//8] |= start mask\n",
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" Set screen[x2//8] |= end mask\n",
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"</pre>\n",
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"\n",
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"Complexity:\n",
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"* Time: O(length of screen)\n",
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"* Space: O(1)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"class BitsScreen(object):\n",
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"\n",
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" def draw_line(self, screen, width, x1, x2):\n",
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" if None in (screen, width, x1, x2):\n",
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" raise TypeError('Invalid argument: None')\n",
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" if not screen or not width:\n",
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" raise ValueError('Invalid arg: Empty screen or width')\n",
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" MAX_BIT_VALUE = len(screen) * 8\n",
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" if x1 < 0 or x2 < 0 or x1 >= MAX_BIT_VALUE or x2 >= MAX_BIT_VALUE:\n",
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" raise ValueError('Invalid arg: x1 or x2 out of bounds')\n",
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" start_bit = x1 % 8\n",
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" end_bit = x2 % 8\n",
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" first_full_byte = x1 // 8\n",
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" if start_bit != 0:\n",
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" first_full_byte += 1\n",
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" last_full_byte = x2 // 8\n",
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" if end_bit != (8 - 1):\n",
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" last_full_byte -= 1\n",
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" for byte in range(first_full_byte, last_full_byte + 1):\n",
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" screen[byte] = int('11111111', base=2)\n",
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" start_byte = x1 // 8\n",
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" end_byte = x2 // 8\n",
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" if start_byte == end_byte:\n",
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" left_mask = (1 << (8 - start_bit)) - 1\n",
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" right_mask = ~((1 << (8 - end_bit - 1)) - 1)\n",
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" mask = left_mask & right_mask\n",
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" screen[start_byte] |= mask\n",
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" else:\n",
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" start_mask = (1 << (8 - start_bit)) - 1\n",
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" end_mask = 1 << (8 - end_bit - 1)\n",
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" screen[start_byte] |= start_mask\n",
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" screen[end_byte] |= end_mask"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Unit Test"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Overwriting test_draw_line.py\n"
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]
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}
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],
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"source": [
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"%%writefile test_draw_line.py\n",
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"from nose.tools import assert_equal\n",
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"\n",
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"\n",
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"class TestBitsScreen(object):\n",
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"\n",
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" def test_draw_line(self):\n",
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" bits_screen = BitsScreen()\n",
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" screen = []\n",
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" for _ in range(20):\n",
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" screen.append(int('00000000', base=2))\n",
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" bits_screen.draw_line(screen, width=32, x1=68, x2=80)\n",
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" assert_equal(screen[8], int('00001111', base=2))\n",
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" assert_equal(screen[9], int('11111111', base=2))\n",
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" assert_equal(screen[10], int('10000000', base=2))\n",
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" bits_screen.draw_line(screen, width=32, x1=2, x2=6)\n",
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" assert_equal(screen[0], int('00111110', base=2))\n",
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" bits_screen.draw_line(screen, width=32, x1=10, x2=13)\n",
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" assert_equal(screen[1], int('00111100', base=2))\n",
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" print('Success: test_draw_line')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestBitsScreen()\n",
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" test.test_draw_line()\n",
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"\n",
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"\n",
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"if __name__ == '__main__':\n",
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" main()"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"metadata": {
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"collapsed": false
|
||||
},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
|
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"Success: test_draw_line\n"
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]
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}
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],
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"source": [
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"%run -i test_draw_line.py"
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]
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}
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],
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"metadata": {
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"kernelspec": {
|
||||
"display_name": "Python 3",
|
||||
"language": "python",
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||||
"name": "python3"
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||||
},
|
||||
"language_info": {
|
||||
"codemirror_mode": {
|
||||
"name": "ipython",
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||||
"version": 3
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||||
},
|
||||
"file_extension": ".py",
|
||||
"mimetype": "text/x-python",
|
||||
"name": "python",
|
||||
"nbconvert_exporter": "python",
|
||||
"pygments_lexer": "ipython3",
|
||||
"version": "3.4.3"
|
||||
}
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||||
},
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||||
"nbformat": 4,
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"nbformat_minor": 0
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||||
}
|
||||
28
bit_manipulation/draw_line/test_draw_line.py
Normal file
28
bit_manipulation/draw_line/test_draw_line.py
Normal file
@ -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()
|
||||
Loading…
x
Reference in New Issue
Block a user