# Thread: Lempel Ziv question

1. ## Lempel Ziv question

Hello everybody here, this is my first post to this forum. Hopefully to get the help
I'm trying to understand the mechanism of encoding by using Lempel ziv algorithm. But I'm only able to understand how to do the first step. which is for example:
123456653131455
1, 2, 3, 4, 5, 6, 65, 31, 314, 45, 5
then I assign places (index) for every phrase
0 0
1 1
2 2
3 3
4 4
5 5
6 6
65 7
and so on. It is also probably to be wrong in assigning indexes.
the question is how I can complete the whole table as I need to prepare for my exam and up till now not able to figure out the idea. how to obtain the dictionary content, pointer,element (0,0 0,1 4,5 and so on), fixed length code and base 5 pointer and element

2. Your question is a bit hard to understand, but it seems to be about LZ78 or LZW,
while more common LZ algorithms are LZ77, which work differently.
Anyway, you can read about LZW in http://en.wikipedia.org/wiki/Lempel%...Welch#Encoding

3. I think LZ dictionary, can any one explain it? thnks

4. thanks for ur reply. can anyone explain me the table below?
I want to know how can I identify the highlighted row? the source code is (1, 0, 10, 11, 01, 101, 010, 1011)

is there any standard way to identify that? I tried to read so many resources about that but they are all confusing.

5. Hello, Guys. I got the point .
I will explain it for everyone who did not understand the point.
We have two elements (Pointer which is the bit in the left side, and the bit which is in the right side.
We start with Null because nothing happened yet. Then the second row (0,1) means that bit #1 was the first time appears so we assign the value zero in the pointer and the second number which is 1 is for the last bit in the right side. then the third column which is zero, the zero is first time appears then the last bit (which is the only one) is zero so the value will be (0,0).
Now we have just two bits (0, 1) and we have already seen both of them. the fourth row which is 10 as we already seen bit number 1, we find find its place in the dictionary place which is 1 and the last digit is 0 so the pointer and bit will be (1, 0). And so on
Thanks for taking time to read this post,

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