Question

CSE 002: Fundamentals of Programming
Spring 2020$image?w=619&h=1&rev=1&ac=1&parent=1-6XAL$$image?w=619&h=1&rev=1&ac=1&parent=1-6XAL$

Homework Assignment 6:

Objectives. The objective of this homework is to give you practice with writing while, for, and do-while loops.

You may find it helpful to work through the check point questions embedded in the chapter, and to practice on homework problems from the text that we have not assigned. Note that solutions to the even-numbered problems are available on the book’s student resource website as described on page xii.

All homework is checked for evidence of plagiarism. Academic dishonesty carries a tremendous penalty, and offenders will be caught. Copying homework will result in a minimum of your failure of this class, and can include expulsion from Lehigh, and worse. See the syllabus for a clear guide on collaboration.

Assignment 1) Write a program that asks the user for two integers: Length and Width. Length is to specify how many characters the following pattern should spread, horizontally, across the screen. Width should specify how many characters the following pattern should spread, vertically, across the screen. The input on the screen might look like this:

Input your desired length: Bazooka!

  Error: please type in an integer.

Input your desired length: 39

Input your desired width: 7

# /\ ## /\ ## /\   

# / \ # # / \ # # / \  

  # / \ # # / \ # # / \

   # \ # \ # \

  / # # \ / # # \ / # #

/ # # \ / # # \ / # #  

/ ## \/ ## \/ ##   

Here is another example:

Input your desired length: 45

Input your desired width: 54

  Error: Please input an integer smaller than the length.

Input your desired width: 4

# /\ ## /\ ## /\ ## /\ ## /\ ## /\

#/ \# #/ \# #/ \# #/ \# #/ \# #/  

/# #\ /# #\ /# #\ /# #\ /# #\ /#  

/ ## \/ ## \/ ## \/ ## \/ ## \/ ##

Some details on this pattern: The pattern is always composed of two twists, a slash-based twist, and a hashtag-based twist. When the desired width is odd, then the hashtag and the slash alternate in front (see first example).

Reject any input where the requested width is larger than the requested length, or when the requested length is greater than 80. Original UNIX terminals displayed at most 80 characters, hence the limit.

Hints:

• The helices displayed can be thought of as a series of “X” patterns, where each pattern is width characters tall (vertically) and width characters long (horizontally). Note that there are two variations on the X pattern - the first pattern involves the hashtags going down and to the right, and the slashes going up and to the right. The second X pattern has the slashes going down and to the right, and hashes going up and to the right. The two patterns alternate.

  • The fact that the patterns repeat means that you can use modulus arithmetic to figure out which “X” a given character is in.

• When printing out any pattern, you must generate the whole line - including spaces. To generate the pattern, imagine that you are typing out the characters along one line, adding spaces or slashes or hashtags to it. What are the mathematical rules that relate to that?

• You can generate the pattern with two nested loops - one that controls how many lines are generated, and the second that generates the characters on each line.

• Some students have been having trouble with testing for errors in input. Since the user can just keep inputting erroneous inputs forever, you need to have an infinite loop that gets broken when the user inputs correct data. Here’s an example looking for a double:

//an integer to store the user input

double myDouble = 0.0;

//a switch to decide if you want to ask again

bool acceptable = false;

//loop until you get acceptable input (i.e. if it's a double)

System.out.print("Input your double: ");

while( !acceptable ){

//check if the input is a double.

if (input.hasNextDouble() ){

//if so, store it.

myDouble = input.nextDouble();

acceptable = true;

}

else{

//if not, trash it. This does not assign the output of

//next() to anything. The output is just discarded.

System.out.println(" ERROR: need a double");

System.out.print("Input your double: ");

input.next();

}

}

Suppose that you need to get a positive double. You can add additional tests (i.e. if statements) after you get the nextDouble.

• This homework should reveal how hard it can be to create nested loops that generate complex patterns. After you solve it, as an optional exercise, try recreating the same pattern with for loops, while loops, and do-while loops, so that you can recheck that your abilities are just as strong on all kinds of input.

Store the program in Twisty.java.

Part II: Tracing code and Exam Preparation

Answer the following questions without writing code on your computer. Submit your completed work as a jpg or pdf. Regardless of how you scan it, make sure that it is very legible. Name the file PracticeHW6.pdf and submit it on courseSite.

Write a program that forces the user to enter an integer between 1 and 9, inclusive, and then prints out displays that depend on the value entered and look like the following examples. If a negative integer is provided, the program exits, printing out “ERROR”. Otherwise, the program asks again.

Size: 3 Size: 5 Size: 1 Size: 7

33333 555555555 1 7777777777777

32223 544444445 7666666666667

32123 543333345 Size: -3 7655555555567

32223 543222345 ERROR 7654444444567

33333 543212345 7654333334567

543222345 Size: asd 7654322234567

543333345 Size: 0 7654321234567

544444445 Size: -1 7654322234567

555555555 ERROR 7654333334567

7654444444567
7655555555567

7666666666667

7777777777777