AP Computer Science A Practice Test 6 - Picture and Elevens Labs

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1 AP Computer Science A Practice Test 6 - Picture and Elevens Labs Name Date Period 1) What are the RGB values for a white pixel? R, G, B = 2) a) How many bytes does it take in the RGB color model (including the alpha value) to represent a pixel? b) What primitive data type is best suited to store such a color? 3) Which of these pixels having these RGB values is the brightest? a. (5, 50, 17) b. (80, 80, 80) c. (100, 20, 30) d. (180, 170, 79) e. (70, 100, 180) 4) Assuming a no-argument constructor exists for Picture and SimplePicture, which of the following would not compile? a. DigitalPicture obj = new Picture(); b. DigitalPicture obj = new SimplePicture(); c. Picture obj = new SimplePicture(); d. SimplePicture obj = new Picture(); e. Picture obj = new Picture(); 5) For a 1.8 megapixel (1,800,000 pixels) image with 1500 rows, what are the (r, c) coordinates of the pixel in the lower right corner? (r, c) = ( ) 6) For a pixel array having 36 rows and 22 columns, how many times will the code in code area #1 be executed? for (int row = 34; row < pixels.length; row++) for (int col = 10; col < pixels[0].length; col++) // code area #1 Number of times =

2 7) In the Picture Lab, the following code was used to access and modify a pixel s red color. public class Pixel public int getred() public void setred(int value) a) Write a method int getcountredovervalue(int value) that returns a count of the number of pixels in the current picture that have a red value greater than the parameter value. public int getcountredovervalue(int value) Pixel[][] pixels = this.getpixels2d(); b) Write a method setredtohalfvalueintophalf() that sets the red value for all pixels in the top half of the picture to half their current red value. public void setredtohalfvalueintophalf() Pixel[][] pixels = this.getpixels2d();

3 8) Which of the following code segments correctly stores in int variable r1 and r2 random unequal integers, each of which can be between 0 and n-1, inclusive? Circle all that are correct. (A) r1 = (int)(math.random() * n - 1); (B) r1 = (int)(math.random() * (n - 1)); r2 = (int)(math.random() * (n - 1)); if(r1 == r2) r2 = (int)(math.random() * (n - 1)); r1 = (int)(math.random() * n); if(r1 == r2) (D) r1 = (int)(math.random() * (n - 1)); while(r1 == r2) r1 = (int)(math.random() * n); while(r1 == r2) 9) Consider the following declarations where... is a valid Board constructor parameter list. I. Board board = new Board(...); II. Board board = new ElevensBoard(); III. ElevensBoard board = new ElevensBoard(); Which of the declarations above is(are) valid? (A) (B) (D) I only I and II only I and III only II and III only I, II, and III 10) Consider the first line of the ElevensBoard class declaration below. public class ElevensBoard extends Board Which of the following methods must be implemented as a result of the way the ElevensBoard class has been declared? I. tostring II. anotherplayispossible III. islegal IV. dealmycards (A) (B) (D) I only I, II, and IV only II and III only I and IV only I, II, III, and IV

4 11) Consider the Deck class on the Code Sheet, related to the Elevens Lab. Comments are omitted, and the tostring implementation is not shown, to save space. Write an "efficient selection shuffle" that efficiently shuffles the deck. Use these general guidelines: Loop through the cards in the deck, starting at the end of the deck and working your way down. Use a structure similar to a selection sort, and reset the size at the end of the method. /** * Randomly permute the given collection of cards using the structure of a selection * sort, starting at the end of the deck. Reset the size to represent the entire deck. */ public void shuffle() 12) Consider a game related to Elevens, called Nines, that uses a 9-card board. Ace, 2,, 8, 9, 10, jack, queen, king correspond to the point values of 1, 2,, 8, 9, 0, 0, 0, 0. Pairs of cards whose point values add up to 9 can be selected and removed. Nines can be removed singly. A group of four cards, 10, jack, queen, king, can be selected and removed. For the game of Nines, write the method findsinglenineorpairsumnine. This method should be passed a List of Integer (selectedcards), representing indexes for the cards to be checked. The method should return true if the board entries in selectedcards contain a single 9 or a 9-pair. The method should return false otherwise. (cont)

5 /** * Look for a 9-pair in the selected cards, or a single 9. selectedcards selects a subset of this board. It is a list * of indexes into this board that are searched * to find a 9-pair or a single 9. true if the board entries in selectedcards * contain a 9-pair or a single 9; false otherwise. */ private boolean findsinglenineorpairsumnine (List<Integer> selectedcards) 13) Consider the Card class on the Code Sheet, related to the Elevens Lab. Complete the following printcards method to print all of the elements of cards (one card per line) that are indexed by the cards on the board (these will need to be obtained first). public static printcards(elevensboard board)

Lesson 90: Elevens Lab #3 (W31D3)

Lesson 90: Elevens Lab #3 (W31D3) Balboa High School Michael Ferraro April 6, 2016 1 / 28 Do Now Prepare HW to be checked: Download this driver for questions 1 & 2 on p9, insert your methods, and run.