Which of the following is a possible LZW compression of the message "xyz xyz xyz"?
A) 1234
B) 1234545
C) 232
D) 12

Question

Quizplus · Accepted Answer

LZW compression works by reading a sequence of symbols and when it encounters a new symbol or sequence, it adds it to the dictionary and outputs the code for the previously encountered sequence. For "xyz xyz xyz", the process would start by encoding 'x', 'y', and 'z' individually (assuming 'x', 'y', and 'z' are assigned codes 1, 2, and 3 respectively). When it encounters 'xyz' again, it would have already added 'xyz' as a new entry in its dictionary (let's say with the code 4), so it can now encode the next occurrence of 'xyz' more efficiently. The pattern repeats for the third 'xyz', which can be encoded using the already added dictionary entry. Therefore, "1234545" represents a plausible LZW compression sequence for "xyz xyz xyz", starting with individual characters and then using the dictionary for repeated sequences.

Which of the Following Is a Possible LZW Compression of the Message