interactive-coding-challenges/online_judges/sentence_screen_fit/sentence_screen_fit_solution.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": [
    "# Solution Notebook"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Problem: Find how many times a sentence can fit on a screen.\n",
    "\n",
    "See the [LeetCode](https://leetcode.com/problems/sentence-screen-fitting/) problem page.\n",
    "\n",
    "<pre>\n",
    "Given a rows x cols screen and a sentence represented by a list of non-empty words, find how many times the given sentence can be fitted on the screen.\n",
    "\n",
    "Note:\n",
    "\n",
    "A word cannot be split into two lines.\n",
    "The order of words in the sentence must remain unchanged.\n",
    "Two consecutive words in a line must be separated by a single space.\n",
    "Total words in the sentence won't exceed 100.\n",
    "Length of each word is greater than 0 and won't exceed 10.\n",
    "1 ≤ rows, cols ≤ 20,000.\n",
    "Example 1:\n",
    "\n",
    "Input:\n",
    "rows = 2, cols = 8, sentence = [\"hello\", \"world\"]\n",
    "\n",
    "Output: \n",
    "1\n",
    "\n",
    "Explanation:\n",
    "hello---\n",
    "world---\n",
    "\n",
    "The character '-' signifies an empty space on the screen.\n",
    "Example 2:\n",
    "\n",
    "Input:\n",
    "rows = 3, cols = 6, sentence = [\"a\", \"bcd\", \"e\"]\n",
    "\n",
    "Output: \n",
    "2\n",
    "\n",
    "Explanation:\n",
    "a-bcd- \n",
    "e-a---\n",
    "bcd-e-\n",
    "\n",
    "The character '-' signifies an empty space on the screen.\n",
    "Example 3:\n",
    "\n",
    "Input:\n",
    "rows = 4, cols = 5, sentence = [\"I\", \"had\", \"apple\", \"pie\"]\n",
    "\n",
    "Output: \n",
    "1\n",
    "\n",
    "Explanation:\n",
    "I-had\n",
    "apple\n",
    "pie-I\n",
    "had--\n",
    "\n",
    "The character '-' signifies an empty space on the screen.\n",
    "</pre>\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 sentence is ASCII?\n",
    "    * Yes\n",
    "* Can we assume the inputs are valid?\n",
    "    * No\n",
    "* Is the output an integer?\n",
    "    * Yes\n",
    "* Can we assume this fits memory?\n",
    "    * Yes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Test Cases\n",
    "\n",
    "* None -> TypeError\n",
    "* rows < 0 or cols < 0 -> ValueError\n",
    "* cols = 0 -> 0\n",
    "* sentence = '' -> 0\n",
    "* rows = 2, cols = 8, sentence = [\"hello\", \"world\"] -> 1\n",
    "* rows = 3, cols = 6, sentence = [\"a\", \"bcd\", \"e\"] -> 2\n",
    "* rows = 4, cols = 5, sentence = [\"I\", \"had\", \"apple\", \"pie\"] -> 1"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Algorithm\n",
    "\n",
    "It can be relatively straightforward to come up with the brute force solution, check out the method `count_sentence_fit_brute_force` below.  \n",
    "\n",
    "The optimized solutions is discussed in more depth [here](https://discuss.leetcode.com/topic/62455/21ms-18-lines-java-solution/25).\n",
    "\n",
    "<pre>\n",
    "rows = 4\n",
    "cols = 6\n",
    "sentence = ['abc', 'de', 'f']\n",
    "\n",
    "\"abc de f abc de f abc de f ...\" // start=0\n",
    " 012345                          // start=start+cols+adjustment=0+6+1=7 (1 space removed in screen string)\n",
    "        012345                   // start=7+6+0=13\n",
    "              012345             // start=13+6-1=18 (1 space added)\n",
    "                   012345        // start=18+6+1=25 (1 space added)\n",
    "                          012345\n",
    "</pre>\n",
    "\n",
    "Complexity:\n",
    "* Time: O(1)\n",
    "* Space: O(1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Code"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "class Solution(object):\n",
    "\n",
    "    def count_sentence_fit_brute_force(self, sentence, rows, cols):\n",
    "        if sentence is None:\n",
    "            raise TypeError('sentence cannot be None')\n",
    "        if rows is None or cols is None:\n",
    "            raise TypeError('rows and cols cannot be None')\n",
    "        if rows < 0 or cols < 0:\n",
    "            raise ValueError('rows and cols cannot be negative')\n",
    "        if cols == 0 or not sentence:\n",
    "            return 0\n",
    "        curr_row = 0\n",
    "        curr_col = 0\n",
    "        count = 0\n",
    "        while curr_row < cols:\n",
    "            for word in sentence:\n",
    "                # If the current word doesn't fit on the current line,\n",
    "                # move to the next line\n",
    "                if len(word) > cols - curr_col:\n",
    "                    curr_col = 0\n",
    "                    curr_row += 1\n",
    "                # If we are beyond the number of rows, return\n",
    "                if curr_row >= rows:\n",
    "                    return count\n",
    "                # If the current word fits on the current line,\n",
    "                # 'insert' it here\n",
    "                if len(word) <= cols - curr_col:\n",
    "                    curr_col += len(word) + 1\n",
    "                # If it still doesn't fit, then the word is too long\n",
    "                # and we should just return the current count\n",
    "                else:\n",
    "                    return count\n",
    "            count += 1\n",
    "        return count\n",
    "\n",
    "    def count_sentence_fit(self, sentence, rows, cols):\n",
    "        if sentence is None:\n",
    "            raise TypeError('sentence cannot be None')\n",
    "        if rows is None or cols is None:\n",
    "            raise TypeError('rows and cols cannot be None')\n",
    "        if rows < 0 or cols < 0:\n",
    "            raise ValueError('rows and cols cannot be negative')\n",
    "        if cols == 0 or not sentence:\n",
    "            return 0\n",
    "        string = ' '.join(sentence) + ' '\n",
    "        start = 0\n",
    "        str_len = len(string)\n",
    "        for row in range(rows):\n",
    "            start += cols\n",
    "            # We don't need extra space for the current row\n",
    "            if string[start % str_len] == ' ':\n",
    "                start += 1\n",
    "            # The current row can't fit, so we'll need to \n",
    "            # remove characters from the next word\n",
    "            else:\n",
    "                while (start > 0 and string[(start - 1) % str_len] != ' '):\n",
    "                    start -= 1\n",
    "        return start // str_len"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Overwriting test_count_sentence_fit.py\n"
     ]
    }
   ],
   "source": [
    "%%writefile test_count_sentence_fit.py\n",
    "import unittest\n",
    "\n",
    "\n",
    "class TestSolution(unittest.TestCase):\n",
    "\n",
    "    def test_count_sentence_fit(self):\n",
    "        solution = Solution()\n",
    "        self.assertRaises(TypeError, solution.count_sentence_fit, \n",
    "                      None, None, None)\n",
    "        self.assertRaises(ValueError, solution.count_sentence_fit, \n",
    "                      'abc', rows=-1, cols=-1)\n",
    "        sentence = [\"hello\", \"world\"]\n",
    "        expected = 1\n",
    "        self.assertEqual(solution.count_sentence_fit(sentence, rows=2, cols=8),\n",
    "                     expected)\n",
    "        sentence = [\"a\", \"bcd\", \"e\"]\n",
    "        expected = 2\n",
    "        self.assertEqual(solution.count_sentence_fit(sentence, rows=3, cols=6),\n",
    "                     expected)\n",
    "        sentence = [\"I\", \"had\", \"apple\", \"pie\"]\n",
    "        expected = 1\n",
    "        self.assertEqual(solution.count_sentence_fit(sentence, rows=4, cols=5),\n",
    "                     expected)\n",
    "        print('Success: test_count_sentence_fit')\n",
    "\n",
    "\n",
    "def main():\n",
    "    test = TestSolution()\n",
    "    test.test_count_sentence_fit()\n",
    "\n",
    "\n",
    "if __name__ == '__main__':\n",
    "    main()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Success: test_count_sentence_fit\n"
     ]
    }
   ],
   "source": [
    "%run -i test_count_sentence_fit.py"
   ]
  }
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