Homework 8 for Computer Science 125

Introduction to Computer Science

Boise State University, Spring 1999

Warm-up and Practice Problems

• CCJ: Exercise R9.4, p 413.
• CCJ: Exercise R9.7, p 413.
• CCJ: Exercise R9.8, p 414.
• CCJ: Exercise R9.9, p 414.
• CCJ: Exercise R9.13, p 413.
• CCJ: Exercise R9.14, p 413.
• CCJ: Exercise R9.15, p 414.
• CCJ: Exercise R10.1, p 445.
• CCJ: Exercise R10.12, p 446.
• CCJ: Exercise R10.13, p 446.
• CCJ: Exercise R11.3, p 472.
• CCJ: Exercise R11.7, p 472.
• CCJ: Exercise R11.16, p 473.
• Ethics: Consider the Challenger Disaster as presented here (by Texas A&M University Engineering Ethics). Who is responsible? What should, or could, the engineers have done differently?

Graded Problems

P23. (NPR Puzzle) Write a program that takes the name of a word file and a desired score. These input parameters can be given at the command line:

 > java Program23 wordFile 225 

where the first argument is the name of the file and the second is the desired score. If the user does not provide arguments when calling the program, that is, they invoke the program with the command:

 > java Program23 

prompt the user for the the name of the file, then for the desired score.

The program then prints out all words with that score from that given file. To assign a score to word, first assign a number to each letter: 1 to A, 2 to B, 3 to C, etc. Then, the score of the word is the product of the numbers assigned to the letters. For example, the score of cab is 3*1*2 = 6.

For example, if the file wordy contains:

cab

bat

batty

cat

cats

mat

mate

gate

agate

and the user types in the command:

 > java Program23 wordy 700 

The program prints:

 The following words have a score of 700:
	gate
	agate 

Submit this as program 23 using the electronic submission. Please call the file (and the class) Program23.

Hint: To assign a number to each letter, use the method indexOf on the string "*ABCDEFGHIJKLMNOPQRSTUVWXYZ". For example,

	"*ABCDEFGHIJKLMNOPQRSTUVWXYZ".indexOf("C")
	

is 3. See Section 11.6, p 468 for an example of using indexOf.

(See NPR's Weekend Edition for a related puzzler (28 March 1999)).

P24. (GPA Calculator) In plain java, write a GPA calculator that allows the user to enter the grade and the credit hour of their courses, and then calculates their GPA. The calculator should include a clear button that clears all previously entered scores, a choice button for the letter grade, a choice for the number of credit hours, and a submit button that records their entry, displays the current GPA, and resets the choice buttons. For example:


Follow the javadoc comments for this applet when setting up your program.

Submit this as program 24 using the electronic submission. Please call the file (and the class) Program24. Include an HTML file called Program24.html to display your applet.

Hints:

• See the plain java web page for some example programs that write to the screen.
• Remember to change the color to "clear" the screen and to write to the screen.
• The method, Integer.parseInt() takes a string and returns the integer it represents.

P25. (Merge sort, using sortedMerge) Write a program that:
1. Asks the user for the number of integers in their list.
2. Reads in those elements.
3. Calls a function called sort that sorts the list.
4. Prints out the list of numbers.
The sort function should split the list of numbers into two lists of about the same length, sort each of these lists, and then merge the lists together, using mergedSorted (P21 from Homework 7). Submit this as program 25 using the electronic submission. Please call the file (and the class) Program25.