03-Methods and Functions/04-Function Practice Exercises - Solutions.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Function Practice Exercises - Solutions\n",
    "\n",
    "Problems are arranged in increasing difficulty:\n",
    "* Warmup - these can be solved using basic comparisons and methods\n",
    "* Level 1 - these may involve if/then conditional statements and simple methods\n",
    "* Level 2 - these may require iterating over sequences, usually with some kind of loop\n",
    "* Challenging - these will take some creativity to solve"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## WARMUP SECTION:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### LESSER OF TWO EVENS: Write a function that returns the lesser of two given numbers *if* both numbers are even, but returns the greater if one or both numbers are odd\n",
    "    lesser_of_two_evens(2,4) --> 2\n",
    "    lesser_of_two_evens(2,5) --> 5"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def lesser_of_two_evens(a,b):\n",
    "    if a%2 == 0 and b%2 == 0:\n",
    "        return min(a,b)\n",
    "    else:\n",
    "        return max(a,b)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "2"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "lesser_of_two_evens(2,4)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "5"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "lesser_of_two_evens(2,5)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### ANIMAL CRACKERS: Write a function takes a two-word string and returns True if both words begin with same letter\n",
    "    animal_crackers('Levelheaded Llama') --> True\n",
    "    animal_crackers('Crazy Kangaroo') --> False"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def animal_crackers(text):\n",
    "    wordlist = text.split()\n",
    "    return wordlist[0][0] == wordlist[1][0]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "animal_crackers('Levelheaded Llama')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "animal_crackers('Crazy Kangaroo')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### MAKES TWENTY: Given two integers, return True if the sum of the integers is 20 *or* if one of the integers is 20. If not, return False\n",
    "\n",
    "    makes_twenty(20,10) --> True\n",
    "    makes_twenty(12,8) --> True\n",
    "    makes_twenty(2,3) --> False"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def makes_twenty(n1,n2):\n",
    "    return (n1+n2)==20 or n1==20 or n2==20"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "makes_twenty(20,10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "makes_twenty(20,10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "#Check\n",
    "makes_twenty(2,3)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# LEVEL 1 PROBLEMS"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### OLD MACDONALD: Write a function that capitalizes the first and fourth letters of a name\n",
    "     \n",
    "    old_macdonald('macdonald') --> MacDonald\n",
    "    \n",
    "Note: `'macdonald'.capitalize()` returns `'Macdonald'`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def old_macdonald(name):\n",
    "    if len(name) > 3:\n",
    "        return name[:3].capitalize() + name[3:].capitalize()\n",
    "    else:\n",
    "        return 'Name is too short!'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'MacDonald'"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "old_macdonald('macdonald')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### MASTER YODA: Given a sentence, return a sentence with the words reversed\n",
    "\n",
    "    master_yoda('I am home') --> 'home am I'\n",
    "    master_yoda('We are ready') --> 'ready are We'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def master_yoda(text):\n",
    "    return ' '.join(text.split()[::-1])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'home am I'"
      ]
     },
     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "master_yoda('I am home')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'ready are We'"
      ]
     },
     "execution_count": 14,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "master_yoda('We are ready')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### ALMOST THERE: Given an integer n, return True if n is within 10 of either 100 or 200\n",
    "\n",
    "    almost_there(90) --> True\n",
    "    almost_there(104) --> True\n",
    "    almost_there(150) --> False\n",
    "    almost_there(209) --> True\n",
    "    \n",
    "NOTE: `abs(num)` returns the absolute value of a number"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def almost_there(n):\n",
    "    return ((abs(100 - n) <= 10) or (abs(200 - n) <= 10))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "almost_there(104)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "almost_there(150)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 18,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "almost_there(209)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# LEVEL 2 PROBLEMS"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Find 33: \n",
    "\n",
    "Given a list of ints, return True if the array contains a 3 next to a 3 somewhere.\n",
    "\n",
    "    has_33([1, 3, 3]) → True\n",
    "    has_33([1, 3, 1, 3]) → False\n",
    "    has_33([3, 1, 3]) → False"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def has_33(nums):\n",
    "    for i in range(0, len(nums)-1):\n",
    "      \n",
    "      # nicer looking alternative in commented code\n",
    "      #if nums[i] == 3 and nums[i+1] == 3:\n",
    "    \n",
    "      if nums[i:i+2] == [3,3]:\n",
    "        return True  \n",
    "    \n",
    "    return False"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3"
      ]
     },
     "execution_count": 20,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "has_33([1, 3, 3])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### PAPER DOLL: Given a string, return a string where for every character in the original there are three characters\n",
    "    paper_doll('Hello') --> 'HHHeeellllllooo'\n",
    "    paper_doll('Mississippi') --> 'MMMiiissssssiiippppppiii'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def paper_doll(text):\n",
    "    result = ''\n",
    "    for char in text:\n",
    "        result += char * 3\n",
    "    return result"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'HHHeeellllllooo'"
      ]
     },
     "execution_count": 22,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "paper_doll('Hello')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'MMMiiissssssiiissssssiiippppppiii'"
      ]
     },
     "execution_count": 23,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "paper_doll('Mississippi')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### BLACKJACK: Given three integers between 1 and 11, if their sum is less than or equal to 21, return their sum. If their sum exceeds 21 *and* there's an eleven, reduce the total sum by 10. Finally, if the sum (even after adjustment) exceeds 21, return 'BUST'\n",
    "    blackjack(5,6,7) --> 18\n",
    "    blackjack(9,9,9) --> 'BUST'\n",
    "    blackjack(9,9,11) --> 19"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def blackjack(a,b,c):\n",
    "    \n",
    "    if sum((a,b,c)) <= 21:\n",
    "        return sum((a,b,c))\n",
    "    elif sum((a,b,c)) <=31 and 11 in (a,b,c):\n",
    "        return sum((a,b,c)) - 10\n",
    "    else:\n",
    "        return 'BUST'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "18"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "blackjack(5,6,7)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'BUST'"
      ]
     },
     "execution_count": 26,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "blackjack(9,9,9)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "19"
      ]
     },
     "execution_count": 27,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "blackjack(9,9,11)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### SUMMER OF '69: Return the sum of the numbers in the array, except ignore sections of numbers starting with a 6 and extending to the next 9 (every 6 will be followed by at least one 9). Return 0 for no numbers.\n",
    " \n",
    "    summer_69([1, 3, 5]) --> 9\n",
    "    summer_69([4, 5, 6, 7, 8, 9]) --> 9\n",
    "    summer_69([2, 1, 6, 9, 11]) --> 14"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def summer_69(arr):\n",
    "    total = 0\n",
    "    add = True\n",
    "    for num in arr:\n",
    "        while add:\n",
    "            if num != 6:\n",
    "                total += num\n",
    "                break\n",
    "            else:\n",
    "                add = False\n",
    "        while not add:\n",
    "            if num != 9:\n",
    "                break\n",
    "            else:\n",
    "                add = True\n",
    "                break\n",
    "    return total"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "9"
      ]
     },
     "execution_count": 29,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "summer_69([1, 3, 5])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "9"
      ]
     },
     "execution_count": 30,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "summer_69([4, 5, 6, 7, 8, 9])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "14"
      ]
     },
     "execution_count": 31,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "summer_69([2, 1, 6, 9, 11])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# CHALLENGING PROBLEMS"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### SPY GAME: Write a function that takes in a list of integers and returns True if it contains 007 in order\n",
    "\n",
    "     spy_game([1,2,4,0,0,7,5]) --> True\n",
    "     spy_game([1,0,2,4,0,5,7]) --> True\n",
    "     spy_game([1,7,2,0,4,5,0]) --> False\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def spy_game(nums):\n",
    "\n",
    "    code = [0,0,7,'x']\n",
    "    \n",
    "    for num in nums:\n",
    "        if num == code[0]:\n",
    "            code.pop(0)   # code.remove(num) also works\n",
    "       \n",
    "    return len(code) == 1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 33,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "spy_game([1,2,4,0,0,7,5])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 34,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "spy_game([1,0,2,4,0,5,7])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 35,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "spy_game([1,7,2,0,4,5,0])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### COUNT PRIMES: Write a function that returns the *number* of prime numbers that exist up to and including a given number\n",
    "    count_primes(100) --> 25\n",
    "\n",
    "By convention, 0 and 1 are not prime."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def count_primes(num):\n",
    "    primes = [2]\n",
    "    x = 3\n",
    "    if num < 2:  # for the case of num = 0 or 1\n",
    "        return 0\n",
    "    while x <= num:\n",
    "        for y in range(3,x,2):  # test all odd factors up to x-1\n",
    "            if x%y == 0:\n",
    "                x += 2\n",
    "                break\n",
    "        else:\n",
    "            primes.append(x)\n",
    "            x += 2\n",
    "    print(primes)\n",
    "    return len(primes)\n",
    "                "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 37,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "25"
      ]
     },
     "execution_count": 37,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Check\n",
    "count_primes(100)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "BONUS: Here's a faster version that makes use of the prime numbers we're collecting as we go!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 38,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def count_primes2(num):\n",
    "    primes = [2]\n",
    "    x = 3\n",
    "    if num < 2:\n",
    "        return 0\n",
    "    while x <= num:\n",
    "        for y in primes:  # use the primes list!\n",
    "            if x%y == 0:\n",
    "                x += 2\n",
    "                break\n",
    "        else:\n",
    "            primes.append(x)\n",
    "            x += 2\n",
    "    print(primes)\n",
    "    return len(primes)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 39,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "25"
      ]
     },
     "execution_count": 39,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "count_primes2(100)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "-----\n",
    "### Just for fun, not a real problem :)\n",
    "\n",
    "#### PRINT BIG: Write a function that takes in a single letter, and returns a 5x5 representation of that letter\n",
    "    print_big('a')\n",
    "    \n",
    "    out:   *  \n",
    "          * *\n",
    "         *****\n",
    "         *   *\n",
    "         *   *\n",
    "HINT: Consider making a dictionary of possible patterns, and mapping the alphabet to specific 5-line combinations of patterns. <br>For purposes of this exercise, it's ok if your dictionary stops at \"E\"."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def print_big(letter):\n",
    "    patterns = {1:'  *  ',2:' * * ',3:'*   *',4:'*****',5:'**** ',6:'   * ',7:' *   ',8:'*   * ',9:'*    '}\n",
    "    alphabet = {'A':[1,2,4,3,3],'B':[5,3,5,3,5],'C':[4,9,9,9,4],'D':[5,3,3,3,5],'E':[4,9,4,9,4]}\n",
    "    for pattern in alphabet[letter.upper()]:\n",
    "        print(patterns[pattern])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 43,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "  *  \n",
      " * * \n",
      "*****\n",
      "*   *\n",
      "*   *\n"
     ]
    }
   ],
   "source": [
    "print_big('a')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Great Job!"
   ]
  }
 ],
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