We looked at the frequencies of the characters used in some students' text messages. There were one or two surprises.
I asked students to construct variable length codes for some of the characters using Huffman's algorithm. This gave the new students in the class a chance to catch up. We did that on the board. Some students had slightly different trees. If the small-left-big-right rule is not enforeced then the resulting VLCs are different, albiet with the correct lengths.
We discussed the prefix problem briefly and the overhead of tree transmission.
I explained that Huffman's algorithm requires prior knowledge of the data.
I explained that sometimes special comma codes are used to help the receiver recover if some data is lost in transmission.
Perhaps the word "town" is actually more frequent in text messages say "q". We thought about how whole words could also be given codes.
We finished up a good bit early so that the new students could use the lab time to catch up. But they didn't.
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