updated sol

Mission481Solutions.ipynb

@@ -4,56 +4,90 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Inventory Class"
+    "# Reading the Inventory\n",
+    "\n",
+    "Use the `csv` module to read the `laptops.csv` file and separate the header from the rows."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
+   "execution_count": 4,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['Id', 'Company', 'Product', 'TypeName', 'Inches', 'ScreenResolution', 'Cpu', 'Ram', 'Memory', 'Gpu', 'OpSys', 'Weight', 'Price']\n",
+      "['6571244', 'Apple', 'MacBook Pro', 'Ultrabook', '13.3', 'IPS Panel Retina Display 2560x1600', 'Intel Core i5 2.3GHz', '8GB', '128GB SSD', 'Intel Iris Plus Graphics 640', 'macOS', '1.37kg', '1339']\n",
+      "['7287764', 'Apple', 'Macbook Air', 'Ultrabook', '13.3', '1440x900', 'Intel Core i5 1.8GHz', '8GB', '128GB Flash Storage', 'Intel HD Graphics 6000', 'macOS', '1.34kg', '898']\n",
+      "['3362737', 'HP', '250 G6', 'Notebook', '15.6', 'Full HD 1920x1080', 'Intel Core i5 7200U 2.5GHz', '8GB', '256GB SSD', 'Intel HD Graphics 620', 'No OS', '1.86kg', '575']\n",
+      "['9722156', 'Apple', 'MacBook Pro', 'Ultrabook', '15.4', 'IPS Panel Retina Display 2880x1800', 'Intel Core i7 2.7GHz', '16GB', '512GB SSD', 'AMD Radeon Pro 455', 'macOS', '1.83kg', '2537']\n",
+      "['8550527', 'Apple', 'MacBook Pro', 'Ultrabook', '13.3', 'IPS Panel Retina Display 2560x1600', 'Intel Core i5 3.1GHz', '8GB', '256GB SSD', 'Intel Iris Plus Graphics 650', 'macOS', '1.37kg', '1803']\n"
+     ]
+    }
+   ],
    "source": [
-    "import csv                            # step 1\n",
+    "import csv\n",
     "\n",
-    "class Inventory():                    # step 2\n",
+    "with open('laptops.csv') as f:\n",
+    "    reader = csv.reader(f)\n",
+    "    rows = list(reader)\n",
+    "    header = rows[0]\n",
+    "    rows = rows[1:]\n",
     "    \n",
-    "    def __init__(self, csv_filename): # step 3\n",
-    "        with open(csv_filename) as f: # step 4\n",
-    "            reader = csv.reader(f)\n",
-    "            rows = list(reader)\n",
-    "        self.header = rows[0]         # step 5\n",
-    "        self.rows = rows[1:]\n",
-    "        for row in self.rows:         # step 6\n",
-    "            row[-1] = int(row[-1])"
+    "print(header)\n",
+    "for i in range(5):\n",
+    "    print(rows[i])"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Inventory Class\n",
+    "\n",
+    "Start implementing a class to represent the inventory. It get the name of the CSV file as argument and reads it into `self.header` and `self.rows`."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
-   "metadata": {
-    "scrolled": true
-   },
+   "execution_count": 5,
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "['Id', 'Company', 'Product', 'TypeName', 'Inches', 'ScreenResolution', 'Cpu', 'Ram', 'Memory', 'Gpu', 'OpSys', 'Weight', 'Price_euros']\n",
+      "['Id', 'Company', 'Product', 'TypeName', 'Inches', 'ScreenResolution', 'Cpu', 'Ram', 'Memory', 'Gpu', 'OpSys', 'Weight', 'Price']\n",
       "1303\n"
      ]
     }
    ],
    "source": [
-    "inventory = Inventory('laptops.csv')  # step 7\n",
-    "print(inventory.header)               # step 8\n",
-    "print(len(inventory.rows))            # step 9"
+    "class Inventory():                    # step 1\n",
+    "    \n",
+    "    def __init__(self, csv_filename): # step 2\n",
+    "        with open(csv_filename) as f: # step 3\n",
+    "            reader = csv.reader(f)\n",
+    "            rows = list(reader)\n",
+    "        self.header = rows[0]         # step 4\n",
+    "        self.rows = rows[1:]\n",
+    "        for row in self.rows:         # step 5\n",
+    "            row[-1] = int(row[-1])\n",
+    "\n",
+    "inventory = Inventory('laptops.csv')  # step 6\n",
+    "print(inventory.header)               # step 7\n",
+    "print(len(inventory.rows))            # step 8"
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Finding a Laptop From the Id"
+    "# Finding a Laptop From the Id\n",
+    "\n",
+    "Implement a `get_laptop_from_id()` function that given a laptop identifier find the row corresponding to that laptop."
    ]
   },
   {
@@ -106,12 +140,14 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Improving Id Lookups"
+    "# Improving Id Lookups\n",
+    "\n",
+    "Improve the time complexity of finding a laptop with a given id by precomputing a dictionary that maps laptop ids to rows."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 33,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -143,6 +179,13 @@
     "        return None"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test the code:"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 27,
@@ -167,20 +210,22 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Comparing Performance"
+    "# Comparing Performance\n",
+    "\n",
+    "Compare the performance of both function for id lookup."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 44,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "0.5769174098968506\n",
-      "0.0021619796752929688\n"
+      "0.5884554386138916\n",
+      "0.0024595260620117188\n"
      ]
     }
    ],
@@ -214,7 +259,25 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Two Laptop Promotion"
+    "## Analysis\n",
+    "\n",
+    "We got:\n",
+    "\n",
+    "```text\n",
+    "0.5884554386138916\n",
+    "0.0024595260620117188\n",
+    "```\n",
+    "\n",
+    "We can see a significant improve in performance. If we divide _0.588_ by _0.002_ we see that the new method is about _294_ times faster for this input size."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Two Laptop Promotion\n",
+    "\n",
+    "Write a method that finds whether we can spend a given amount of money by purchasing either one or two laptops."
    ]
   },
   {
@@ -285,7 +348,9 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Optimizing Laptop Promotion"
+    "# Optimizing Laptop Promotion\n",
+    "\n",
+    "Create a faster version of the promotion method by using the techniques we've learned in the course."
    ]
   },
   {
@@ -343,6 +408,13 @@
     "        return False                                 # step 6"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test the code:"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 6,
@@ -367,7 +439,9 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Comparing Performance"
+    "# Comparing Promotion Functions\n",
+    "\n",
+    "Compare the performance of both methods for the promotion."
    ]
   },
   {
@@ -406,6 +480,133 @@
     "print(total_time_no_dict)                                # step 7\n",
     "print(total_time_dict)"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Analysis\n",
+    "\n",
+    "We got:\n",
+    "\n",
+    "```text\n",
+    "0.7781209945678711\n",
+    "0.0003719329833984375\n",
+    "```\n",
+    "\n",
+    "We can see a significant improve in performance. If we divide _0.7781_ by _0.0002_ we see that the new method is about _2593_ times faster for this input size."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Finding Laptops Within a Budget\n",
+    "\n",
+    "Implement a method for finding the range of indexes of laptops that fall within a budget."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 10,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "683\n",
+      "-1\n"
+     ]
+    }
+   ],
+   "source": [
+    "import csv                            \n",
+    "\n",
+    "def row_price(row):\n",
+    "    return row[-1]\n",
+    "\n",
+    "class Inventory():                    \n",
+    "    \n",
+    "    def __init__(self, csv_filename):\n",
+    "        with open(csv_filename) as f: \n",
+    "            reader = csv.reader(f)\n",
+    "            rows = list(reader)\n",
+    "        self.header = rows[0]        \n",
+    "        self.rows = rows[1:]\n",
+    "        for row in self.rows:              \n",
+    "            row[-1] = int(row[-1])\n",
+    "        self.id_to_row = {}                        \n",
+    "        for row in self.rows:                       \n",
+    "            self.id_to_row[row[0]] = row\n",
+    "        self.prices = set()                          \n",
+    "        for row in self.rows:                        \n",
+    "            self.prices.add(row[-1])\n",
+    "        self.rows_by_price = sorted(self.rows, key=row_price) # Step 1\n",
+    "    \n",
+    "    def get_laptop_from_id(self, laptop_id):\n",
+    "        for row in self.rows:                 \n",
+    "            if row[0] == laptop_id:\n",
+    "                return row\n",
+    "        return None   \n",
+    "    \n",
+    "    def get_laptop_from_id_fast(self, laptop_id):  \n",
+    "        if laptop_id in self.id_to_row:           \n",
+    "            return self.id_to_row[laptop_id]\n",
+    "        return None\n",
+    "\n",
+    "    def check_promotion_dollars(self, dollars):    \n",
+    "        for row in self.rows:                   \n",
+    "            if row[-1] == dollars:\n",
+    "                return True\n",
+    "        for row1 in self.rows:                  \n",
+    "            for row2 in self.rows:\n",
+    "                if row1[-1] + row2[-1] == dollars:\n",
+    "                    return True\n",
+    "        return False                        \n",
+    "    \n",
+    "    def check_promotion_dollars_fast(self, dollars):\n",
+    "        if dollars in self.prices:                   \n",
+    "            return True\n",
+    "        for price in self.prices:                    \n",
+    "            if dollars - price in self.prices:\n",
+    "                return True\n",
+    "        return False                                \n",
+    "    \n",
+    "    def find_laptop_with_price(self, target_price):\n",
+    "        range_start = 0                                   \n",
+    "        range_end = len(self.rows_by_price) - 1                       \n",
+    "        while range_start < range_end:\n",
+    "            range_middle = (range_end + range_start) // 2  \n",
+    "            value = self.rows_by_price[range_middle][-1]\n",
+    "            if value == target_price:                            \n",
+    "                return range_middle                        \n",
+    "            elif value < target_price:                           \n",
+    "                range_start = range_middle + 1             \n",
+    "            else:                                          \n",
+    "                range_end = range_middle - 1 \n",
+    "        if self.rows_by_price[range_start][-1] != target_price:                  \n",
+    "            return -1                                      \n",
+    "        return range_start\n",
+    "    \n",
+    "    def find_first_laptop_more_expensive(self, target_price): # Step 2\n",
+    "        range_start = 0                                   \n",
+    "        range_end = len(self.rows_by_price) - 1                   \n",
+    "        while range_start < range_end:\n",
+    "            range_middle = (range_end + range_start) // 2  \n",
+    "            price = self.rows_by_price[range_middle][-1]\n",
+    "            if price > target_price:\n",
+    "                range_end = range_middle\n",
+    "            else:\n",
+    "                range_start = range_middle + 1\n",
+    "        if self.rows_by_price[range_start][-1] <= target_price:                  \n",
+    "            return -1                                   \n",
+    "        return range_start\n",
+    "\n",
+    "inventory = Inventory('laptops.csv')                     # Step 3            \n",
+    "print(inventory.find_first_laptop_more_expensive(1000))  # Step 4\n",
+    "print(inventory.find_first_laptop_more_expensive(10000)) # Step 5\n"
+   ]
   }
  ],
  "metadata": {