Lab 4: Strings/While Loops Due Sun, Apr 17 at midnight

Transcription

1 Lab 4: Strings/While Loops Due Sun, Apr 17 at midnight For this lab, you must work with a partner. You should choose a new partner. Remember to turn in your peer review. All functions should be commented appropriately. Create a file called lab4.py. Include as comments your name, your partner s name, class time, TA s name, and lab due date. Then include and comment the following functions: Note: Unless otherwise noted, always include comments for each function that include the input type(s), the output type, how your function calculates, and then at least two test cases. If test cases aren t possible because of random numbers or user input, then give examples of what should happen. Attendance week 1: 2 pts Attendance week 2: 2 pts Part 1: Convert the following recursive functions to while loops: # Problem 1 (2 pts) def f(x,y): if (x == 0): return(y) return(f(x-1,y+x)) print(f(5,0)) #Problem 2: (3 pts) def g(x,y): if y == len(x): print() return print(x[y],end = ", ") return(g(x,y+1)) k = "cats" g(k,0) #Problem 3: (3 pts) def h(x,y,a,b): if x == 5: return y if (x % 2 == 1): k = randrange(0,len(a)) return h(x+1,y+ a[k],a,b) k = randrange(0,len(b)) return h(x+1,y+ b[k],a,b) print(h(0,"","aeiou","bcdfghjklmnpqrstvwxyz"))

2 #Problem 4: (3 pts) def j(x,y,z): if y == 0: return z k = randrange(0,len(x)) if x[k] not in z: return(j(x,y-1,z+ x[k])) return(j(x,y,z)) print(j("vampire",len("vampire"),"")) #Problem 5 (3 pts) def k(x,y): if (x < 0): return k(x*-1,y) elif (x < 10): return(y) return k(x//10,y+1) print(k(-28417,1)) #Problem 6: (4 pts) Note: for this problem, you could convert the number to a string, #and then use 'in'. Don't do that. Use a while loop instead. Don't use #break. def m(x,y): if (x <= 0): return False if (x%10 == y): return True return m(x//10,y) print(m(3214,2)) print(m(4231,5)) Part 2: Do the following using While loops (no recursion!) #Problem 7. (5 pts) When I was a kid, I used to speak a language we called gibberish to my friend when we didn t want adults to understand us. For this language, every vowel would be replaced with ithag and then the vowel. So, for instance, For instance, the word cat would become cithagat Monkey would become mithagonkithagey Write the comments with input, output, and test cases for a function that uses a while loop to create a new word in the gibberish language. So every time a vowel is encountered in a word, it is replaced with ithag,then the vowel, then the rest of the word. Problem 8: (5 pts) Many digital identification numbers such as ISBNs, credit card numbers, bank routing numbers, and UPCs, and even routing packets, are designed with an extra bit, known as a parity bit, that helps detect (and sometimes correct) human entry errors. In this problem we will modify this a bit to

3 assume a simple check-digit algorithm: Parity will be determined by adding all the digits in the number up, minus the last digit (the right-most digit). If the digits add up to an even number and the right-most digit is a 0, then the number is most likely okay. If all the digits add up to an odd number and the right-most digit is a 1, then most likely the number is okay. If the digits don t match the parity number, then the number has probably been corrupted. If the parity number is anything other than a 1 or a 0, the parity number has been corrupted, Otherwise, as far as we know, the number is okay. Write a function (including comments) that uses a while loop to check the number s validity using the above checking system. This function will return a Boolean value. Problem 9: Simple encryption. Part a: (6 pts)you re going to take the alphabet (as a string) and create a new, randomly scrambled version of the alphabet. Each letter must only occur once in the new randomly scrambled version of the alphabet. So, for instance, my input was: z = "abcdefghijklmnopqrstuvwxyz" f9(z,"") and my returned string was: hsyevxgrjlpntfqbzwmkadocui Note: just use all small letters. Let s not deal with capital letters. Side Note: this is something that, when written in its simplest manner, is nicest when written with a while loop. It could end up looping for a long time when trying to find the last few letters that must be added to the encrypted string. We could improve efficiency greatly by creating a new string of leftover letters whenever we ve added over half the letters to the new string. Part b: (7 pts) Now, using the encrypted string above as input to your new function you are about to write, encrypt a word and return that word. For this, the easiest way to do it is to use the index method, which is built into python. Index returns the index of the first occurrence of a character in a string. So, for instance, using the above string z with the alphabet in it, to find the location of the character f in z, you d do the following: ind = z.index( f ) And ind would now hold 5 So, using the encrypted string above, if the input was cat, the returned value would be: yhk. Problem 10: (2 pts) A teacher may want students to practice their multiplication tables. Each week it s a different number. So for instance, one week the students should practice their 4s multiplication tables, and the next week their 6s multiplication tables.

4 Write a function that takes as an input parameter an integer. The function then generates a random number between 0 and 12 including 12. The function then uses the input command to ask the user, what is randnum times x? where randnum is the random number generated, and x is the input parameter. So, for instance, if the input parameter was 5, and the random number generated was 7, the user would be asked, what is 7 times 5? The function should then take the answer the user entered and check whether the user was correct or not, returning a Boolean value with True if the user was correct, and False if the user was wrong. 10b. (5 pts) Now create an online test. This test function will take as an input parameter an integer the test_num) representing number you are testing and an integer representing the number right (num_right) the user must get before they can quit the test. In the function, you will call the function you created above inside a loop. The loop will keep track of the number of times the student answered correctly (e.g., True is returned from the above function). If the student answers num_right correctly in a row, the function returns a string saying Congratulations! You finished! If, however, the student gets one wrong before getting num_right correct in a row, the count starts over at 0. Thus, there is only one way to get out of the loop, and that is for the user to get the answer correct num_right times in a row. Problem 11 Wacky BlackJack: (6 pts) You re going to write a function with a while loop that sort of replicates playing blackjack. Your function should generate random numbers between 1 and 11 until the user enters no in response to the input command, Do you wish to continue?. The user wants to come as close to 21 as possible without going over. (The loop should keep track of the total and print it out before asking if the user wants to continue). Once the user has decided not to continue (they entered, no ), the function should generate another random number (below the loop), this time between 15 and 26 (including 26). This is the dealer s hand. The function should print out the dealer s score. Then, if the Dealer s hand is over 21, the user automatically wins and a string should be returned saying that the user won. If the Dealer s hand is 21 or under, and the user s hand is over 21, the dealer wins and a string should be returned saying that the dealer won. If the dealer s hand is 21 or under and it is greater than the user s hand, a string should be returned saying that the dealer won. If the user s hand is 21 or under and greater than or equal to the dealer s hand (we re giving the user the advantage here), a string should be returned saying that the user won. Part b: (6 pts) Write a function that uses the input function to ask if the user wants to play another round. If they do, it uses a while loop to allow the user to place a bet (again, using the input function). Then call the function in 7a to play a round of wacky blackjack, and keep track of the total amount of money they have while they play (e.g., if they win, they double their bet, and if they lose, they lose it from their total.) Within the loop, the input function must be used to ask if the user wants to play another round. The while loop will continue while the user says yes and has some money left. You can start them out with 100 dollars. (Note: you are in essence calling a loop within a loop here.) Problem 12: Guess the number:

5 Part a (5 pts) Write a recursive function that takes as input parameters a number, and then 2 other numbers x and y, and finally a count parameter. 1. It uses the user input function to ask the user to guess a number between x and y. 2. If the random number is the same as the input parameter number, it returns a count of the number of guesses the computer had to make. 3. If the random number is too high, it first prints (str(randnum) + is too high! ) and then recurses with the range x to y changing so that you only guess between x and the random number (you d have to increase your count). 4. Do the same if the guess is too low. Part b: (7 pts) Now write the same exact function using while loops. Part c: (1 pt) Which is easier, the recursive version or the while loop? Part d: (3 pts) If you choose your guesses wisely, given the range of numbers in which you are guessing (e,g., 0-100, 0-50, etc.) AT MOST how many guesses will you make (hint: how many numbers do you rule out after each guess?) As a mental exercise, in the last lab you created a fractal using recursion. How easy would this be to do using while loops? Problem 13: Nested Loops: For these problems you MUST use nested loops you cannot use string multiplication: Part A(8): Write a non-recursive function that takes as input parameters 2 numbers. It then generates x (the first input parameter) random numbers between 0 and y (the second input parameter). For each random number, it then prints out that many stars across the page (using end = ). So, for example, if the input parameters were 6 and 10, I might get an output looking like this: ****** * **** *** ***** ***** Part B(8): Print out the multiplication tables as follows, if the input parameters are 6 and 4, you d print out: * * * *

6 Note: for this one, you will probably want to use the tab for formatting, e.g., (end= \t ) Part C (10): Now, given an input parameter x, create an x shape using nested loops. So for instance, if the input parameter was 4, you d print out: * Extra Credit (10 pts): Your job: get the string to sum to 100, by inserting in the string two minus symbols and one plus symbol (in any order) to make the formula correct. You aren't allowed to re-arrange digits, or do some toothpick math like combine two minus signs to make a plus. You must use every digit, and all three operators. For example, here's one incorrect solution: = 100 (This is an incorrect formula; it totals 12) You want to write a function that does the thinking for you. It should output every possible equation that can be formed, and the actual result of that equation. The equation(s) that result in 100 should have stars around them. At the end, you should print out the number(s) of formulae that were possible. Here's an excerpt of some example output: = = = = = = possible equations tested Hint: This problem heavily relies on loops and slicing.

7