# Sixth Homework

As usual, you'll do parts of this assignment with a partner, preferably someone you haven't worked with on a prevoius assignment. Be sure to use the Partner App so your partnership is recorded.

#### Part (a)

[This part is repeated from the last assignment.] Don't forget to watch the video Sorting Out Sorting. See the previous assignment for more information.

#### Part (b)

In class we described the (lossless, syntactic) compression method called run-length encoding (RLE). Find three images of flags on the Web: one that will compress very well using RLE, one that will compress very poorly using RLE, and one in the middle. Justify your choices in a few brief sentences (i.e., say why the good one is good, and so on), illustrated with copies of the images. (You'll put your answers to the subsequent parts of the assignment in the same document.)

#### Part (c)

Below are three images. Image A is the original; the other two are compressed using lossy techniques. One uses reduced quantization; the other uses coarser sampling. Which is which? Give a sentence explaining your answer.

#### Part (d)

Below are three graphs representing different series of data. Which series would compress best using delta encoding? Which would compress worst? Again, justify your answer in a sentence or two.

#### Part (e)

(optional) A cryptogram is a message or quotation written in a substitution cipher—for each letter in the original message, a different letter has been uniformly substituted in the cryptogram.

Below is a cryptogram from the Saturday Review. Decode it back into the original English message.

BSL PLXB NFIB CR BSL RDEBDCV DV JFVA VCYLUX DX BSL VCBDEL BSFB BSL ESFIFEBLIX FIL NHILUA DJFKDVFIA. -- RIFVOUDV N. FTFJX

Now ask yourself: What property of natural langauge do cryptograms illustrate? Write your solution to the cryptogram and the one-word answer to this question, marked as part (e) of the document you submit.

Save the document containing your responses to parts (b), (c), (d), and optionally (e) into one document, naming it in the usual form: `hw6-jimb-annw`. Submit this document via Checkmate. Just one partner should submit one copy; the file name and your Email message will let us give both partners credit.

[Parts (b), (c), and (d) written originally by Eamonn Keough.]

Friday, April 6, 2018 9:51 AM