Problem on Vitter algorithm

Hi all,

I have some problems understanding Vitter algorithm. Please consider this example:

http://en.wikipedia.org/wiki/Adaptive_Huffman_coding

suppose the new caracter after "abb" would be "a". So I have to do the update procedure:

1. Go to node 253
2. Now I have to consider if this node does not have the highest number in a block and if no swap it with which has the highest number.

But, this block contains nodes 253 and 254, but 254 does not contain a caracter. So how can I swap them? It is correct If I suppose that a block must contains only nodes with a caracter and caracters are only on leaves nodes? So in this case the block would contain only node 253, so I don't need to swap but only increase the counter and go on with the parent?

Thank you all!

.

Relevant Pages

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