interactive-coding-challenges/recursion_dynamic/max_profit_k/max_profit_challenge.ipynb

{
 "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 stock prices on each consecutive day, determine the max profits with k transactions.\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",
    "* Is k the number of sell transactions?\n",
    "    * Yes\n",
    "* Can we assume the prices input is an array of ints?\n",
    "    * Yes\n",
    "* Can we assume the inputs are valid?\n",
    "    * No\n",
    "* If the prices are all decreasing and there is no opportunity to make a profit, do we just return 0?\n",
    "    * Yes\n",
    "* Should the output be the max profit and days to buy and sell?\n",
    "    * Yes\n",
    "* Can we assume this fits memory?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "<pre>\n",
    "* Prices: None or k: None -> None\n",
    "* Prices: [] or k <= 0 -> []\n",
    "* Prices: [0, -1, -2, -3, -4, -5]\n",
    "    * (max profit, list of transactions)\n",
    "    * (0, [])\n",
    "* Prices: [2, 5, 7, 1, 4, 3, 1, 3] k: 3\n",
    "    * (max profit, list of transactions)\n",
    "    * (10, [Type.SELL day: 7 price: 3, \n",
    "            Type.BUY  day: 6 price: 1, \n",
    "            Type.SELL day: 4 price: 4, \n",
    "            Type.BUY  day: 3 price: 1, \n",
    "            Type.SELL day: 2 price: 7, \n",
    "            Type.BUY  day: 0 price: 2])\n",
    "</pre>"
   ]
  },
  {
   "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": true
   },
   "outputs": [],
   "source": [
    "from enum import Enum  # Python 2 users: Run pip install enum34\n",
    "\n",
    "\n",
    "class Type(Enum):\n",
    "    SELL = 0\n",
    "    BUY = 1\n",
    "\n",
    "\n",
    "class Transaction(object):\n",
    "\n",
    "    def __init__(self, type, day, price):\n",
    "        self.type = type\n",
    "        self.day = day\n",
    "        self.price = price\n",
    "\n",
    "    def __eq__(self, other):\n",
    "        return self.type == other.type and \\\n",
    "            self.day == other.day and \\\n",
    "            self.price == other.price\n",
    "\n",
    "    def __repr__(self):\n",
    "        return str(self.type) + ' day: ' + \\\n",
    "            str(self.day) + ' price: ' + \\\n",
    "            str(self.price)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "class StockTrader(object):\n",
    "\n",
    "    def find_max_profit(self, prices, k):\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_max_profit.py\n",
    "from nose.tools import assert_equal\n",
    "from nose.tools import assert_raises\n",
    "from nose.tools import assert_true\n",
    "\n",
    "\n",
    "class TestMaxProfit(object):\n",
    "\n",
    "    def test_max_profit(self):\n",
    "        stock_trader = StockTrader()\n",
    "        assert_raises(TypeError, stock_trader.find_max_profit, None, None)\n",
    "        assert_equal(stock_trader.find_max_profit(prices=[], k=0), [])\n",
    "        prices = [5, 4, 3, 2, 1]\n",
    "        k = 3\n",
    "        assert_equal(stock_trader.find_max_profit(prices, k), (0, []))\n",
    "        prices = [2, 5, 7, 1, 4, 3, 1, 3]\n",
    "        profit, transactions = stock_trader.find_max_profit(prices, k)\n",
    "        assert_equal(profit, 10)\n",
    "        assert_true(Transaction(Type.SELL,\n",
    "                                day=7,\n",
    "                                price=3) in transactions)\n",
    "        assert_true(Transaction(Type.BUY,\n",
    "                                day=6,\n",
    "                                price=1) in transactions)\n",
    "        assert_true(Transaction(Type.SELL,\n",
    "                                day=4,\n",
    "                                price=4) in transactions)\n",
    "        assert_true(Transaction(Type.BUY,\n",
    "                                day=3,\n",
    "                                price=1) in transactions)\n",
    "        assert_true(Transaction(Type.SELL,\n",
    "                                day=2,\n",
    "                                price=7) in transactions)\n",
    "        assert_true(Transaction(Type.BUY,\n",
    "                                day=0,\n",
    "                                price=2) in transactions)\n",
    "        print('Success: test_max_profit')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestMaxProfit()\n",
    "    test.test_max_profit()\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
}