For this piece of coursework, you will write Java code to answer a number of coding interview style questions. Other weeks will use other programming languages, but as you have done Java, and might not have done much programming over the summer, it's a good piece of revision.
Each question will ask you to write a method that fulfils a given specification. As noted on KEATS, you are encouraged to submit your work early and often. Pushing work to your github repository triggers an automated testing script that will run your code against a set of test cases to give you some feedback, via email, on how you are doing.
After the deadline, your work will be marked by automated testing, to see if it is correct. Marks will be awarded for each test case your code passes. Note that if your code for a given question does not compile, this results in an automatic mark of zero for the question concerned, as it is impossible to test code that cannot run.
There are three sorts of single character edit that can be made to a string:
- Replacing one character with another, at some position
- Removing a character, from some position
- Inserting a character at some position, before what was previously there
Implement the method in the SingleCharacterEdit class (provided) that takes two strings, a and b, and returns a String that prescribes what single-character edit will turn a into b; or returns null if no such single-character edit exists. The format of the string returned should be as follows:
- If the character at position n was replaced with the character c, return the string
replace,n,c. For instance, if character 1 was replaced with an x, returnreplace,1,x - If the character at position n was removed, return
remove,n. For instance, if the first character was removed, returnremove,0. - If a new character c was inserted at position n, return the string
insert,n,c. For instance, for input stringscatandchat, returninsert,1,h
Note the string returned should be exactly as prescribed here. Do not add additional spacing, and replace, remove and insert should be in lowercase.
To test your code, run the given class TestSingleCharacterEdit. This will perform some basic testing of your code, by calling it and checking it gives the right outputs.
Each pixel on a monochrome (black and white) screen can be represted as a bit -- either off (0) or on (1). The whole screen can in turn be represented as an array of bytes, with each byte storing eight pixels (eight bits). The first bytes in the array are the pixels at the left of the top row of the image; and the last bytes in the array are the pixels at the right of last row of the image. For instance, the following image, 16 pixels wide and 3 pixels tall:
1111....1111....
....1111.......1
1111....1111...1
..becomes the bytes (in binary):
{11110000,11110000,00001111,00000001,11110000,11110001}
...or in decimal:
{240,240,15,1,240,241}
When you are ready to test the code you will write for this question, run the given class TestScreenAsBytes. This will perform some basic testing of your code, by calling it and checking it gives the right outputs.
Complete the method setPixel in the given class ScreenAsBytes. This takes as input:
- The bytes representing the screen, as described above
- The width of the image. You can assume this is a multiple of 8. Hint: you can work out the height of the image from the length of the array, and the width.
- The x and y positions of the pixel
The method should modify `screen' so the given pixel has a value of 1. For instance, for a screen 16 pixels wide and 3 pixels tall that is entirely blank (all pixels set to zero), screen would be
00000000,00000000,
00000000,00000000,
00000000,00000000
...or in decimal {0,0,0,0,0,0}. After calling setPixel(screen,16,0,1) to set the first pixel on the second row to 1, screen should be:
00000000,00000000,
10000000,00000000,
00000000,00000000
...or in decimal {0,0,128,0,0,0}
To perform a basic test of your code, run TestScreenAsBytes, which as the first test will set a single pixel of the image to 1 and check the correct one has been set.
Complete the method drawHorizontalLine. This takes as input:
- The bytes representing the image, and its width (like
setPixel) - The start and end X positions of the horizontal line. These should be inclusive -- that is, drawing a line from pixels 0 to 2 on row 1, should set the first three pixels on the row to 1
- The y position at which to draw the line (0 for the first 1, 1 for the next row, and so on)
The method should modify screen to contain a horizontal line drawn at the correct position.
To perform a basic test of your code, run TestScreenAsBytes, which as the second test will draw a horizontal line on the image and check the correct pixels have the value 1.
Complete the method drawVerticalLine. This is the vertical equivalent of drawHorizontalLine line, and takes as input:
- The bytes representing the image, and its width
- The X position at which to draw the vertical line
- The start and end Y positions for the line. As with the horizontal line, these should be inclusive.