Computer Science 15-110, Spring 2011
Class Notes:  Conditionals and Loops Practice (Problem-Solving)

1. Some Basic Functions
1. isSortedString
2. findNthVowel
3. printSquare
4. printDiamond
5. nthPrimeNumber
2. Hangman
3. Sample Solutions

Conditionals and Loops Practice (Problem-Solving)

1. Some Basic Functions
   
1. isSortedString
   Write the function isSortedString that takes a string and returns True if that string is sorted either in non-increasing or non-decreasing order (according to the Unicode values of the characters).   Here are some test cases and some starter code for you:
   
   def isSortedString(s):
       # you write this!
   
   def testIsSortedString():
       print "testingIsSortedString()...",
       assert(isSortedString("CMU") == True)
       assert(isSortedString("UPMC") == True)
       assert(isSortedString("MIT") == False)
       assert(isSortedString("CCMMUU") == True)
       assert(isSortedString("CMUCMU") == False)
       assert(isSortedString("A") == True)
       assert(isSortedString("") == True)
       print "Passed!"
      
   testIsSortedString()
   
   
2. findNthVowel
   Write the function findNthVowel that takes a string and an integer N and returns the index of the Nth vowel in the string, or -1 if there are not N vowels in the string.  Vowels are "A", "E", "I", "O", and "U" (in upper or lower case).  Here are some test cases and some starter code for you:
   
   def findNthVowel(s, n):
       # you write this!
   
   def testFindNthVowel():
       print "Testing findNthVowel()...",
       assert(findNthVowel("AB", 0) == 0)
       assert(findNthVowel("BA", 0) == 1)
       assert(findNthVowel("BA", 1) == -1)
       assert(findNthVowel("ABCDEABCDE", 0) == 0)
       assert(findNthVowel("ABCDEABCDE", 1) == 4)
       assert(findNthVowel("ABCDEABCDE", 2) == 5)
       assert(findNthVowel("ABCDEABCDE", 3) == 9)
       assert(findNthVowel("ABCDEABCDE", 4) == -1)
       assert(findNthVowel("eBCDoIBCDu", 3) == 9)
       assert(findNthVowel("eBCDoIBCDu", 4) == -1)
       print "Passed!"
   
   testFindNthVowel()
   
   
3. printSquare
   Write the function printSquare that takes a non-negative integer N and prints an NxN square of asterisks ("*").  This function is not easily robotically testable (why not?).
   
   
4. printDiamond
   Write the function printDiamond that takes a non-negative integer N and prints an NxN diamond (rotated square) of asterisks ("*").  This function is also not easily robotically testable.
   
   
5. nthPrime
   Write the function nthPrime that takes a non-negative integer N and returns the Nth prime number.  If N is negative, return -1.  Here are some test cases and some starter code for you:
   
   def nthPrime(n):
       # you write this!
   
   def testNthPrime():
       print "Testing nthPrime()...",
       assert(nthPrime(0) == 2)
       assert(nthPrime(1) == 3)
       assert(nthPrime(2) == 5)
       assert(nthPrime(3) == 7)
       assert(nthPrime(4) == 11)
       assert(nthPrime(5) == 13)
       assert(nthPrime(6) == 17)
       assert(nthPrime(7) == 19)
       assert(nthPrime(8) == 23)
       assert(nthPrime(1000) == 7927) # some would say this is the 1001st
       print "Passed!"
   
   testNthPrime()
   
   
2. Hangman
   Write the function playHangman, which takes no parameters and plays a game of Hangman.  Seeing as we have not yet covered random numbers or lists, we will provide you with the function getRandomWord(), which returns a randomly-chosen word (from a list of words that supposedly are good choices for playing Hangman):
   
   # Include all this code in your Hangman solution.
   # Note that the words are in white text here to not give them away
   # (though you'll see them briefly when you copy-paste this text...)
   import time
   def getRandomWord():
       # We have not yet covered lists, so you are not responsible for
       # this function.  But we will use it in our Hangman game.
       words = [ "abbey","abruptly","affix","askew","axiom","azure",
                 "bagpipes","bandwagon","banjo","bayou","blitz","bookworm",
                 "boxcar","boxful","buckaroo","buffalo","buffoon","cobweb",
                 "croquet","daiquiri","disavow","duplex","dwarves",
                 "equip","exodus","fishhook","fixable","foxglove","galaxy",
                 "galvanize","gazebo","gizmo","glowworm","guffaw","haiku",
                 "haphazard","hyphen","icebox","injury","ivory","ivy",
                 "jaundice","jawbreaker","jaywalk","jazzy","jigsaw",
                 "jiujitsu","jockey","jovial","joyful","juicy","jumbo",
                 "kazoo","keyhole","khaki","kilobyte","kiosk","kiwifruit",
                 "knapsack","larynx","luxury","marquis","megahertz",
                 "microwave","mystify","nightclub","nowadays","numbskull",
                 "ovary","oxidize","oxygen","pajama","peekaboo","pixel",
                 "pizazz","pneumonia","polka","quartz","quiz","quorum",
                 "razzmatazz","rhubarb","rickshaw","schizophrenia","sphinx",
                 "spritz","squawk","subway","swivel","topaz","unknown",
                 "unworthy","unzip","uptown","vaporize","vodka","vortex",
                 "walkway","waltz","wavy","waxy","wheezy","whiskey",
                 "whomever","wimpy","wizard","woozy","xylophone",
                 "yachtsman","yippee","youthful","zephyr","zigzag",
                 "zilch","zodiac","zombie"
                 ]
       # Also, we can't use Python's random functions until CLEESE 0.11, so
       # we'll use a not-so-random way to choose a number from 0 to N-1:
       n = len(words)
       randIndex = int(100*time.time()) % n
       return words[randIndex]
   
   
3. Sample Solutions
   Here are some sample solutions to the problems in these notes.

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