Encoding schemes

Im quite new to all this and wondered if someone could help me with this question.

If I had a sequence of aaa...aaa, so a, repeated k times. Which string matching encoding scheme LZ77 or LZ78 would encode this more efficiently? and why?

Here's a description of the algorithms: LZ77 LZ78

Although LZW is probably going to give you better compression with repeated data. GIFs use a modified version of this format. And if your data is very redundant, use the RLE format. That'll reduce your example to just a few bytes.

Then again, this may be a school question. Which is why you need to look at the links and figure it out for yourself.

I have looked at the basics of these two. But im still not sure which one would be more efficient, any ideas?

Your example is trivial. The reason that there are multiple compression methods is that some work better for certain data distributions than others. Surely you can appreciate that a page of textual material presents commonalities of one kind while, say, bitmapped images present another. Give me a string of all "a"s, and as Doggie says, I'll compress the bejaysus out of it with RLE.