peltorator's blog

By peltorator, 5 weeks ago, In English

Hey! I decided to record myself while solving rounds. It's my first attempt and an experiment for my channel. Check out my Educational Round 107 screencast.

Leave a comment if you have anything to say. Did you find it helpful? Is it just a waste of time? Or maybe I should improve something? I've already noticed that in the future I should be aware of the fact that I've got my camera in the right bottom corner so I shouldn't draw there. Maybe you noticed anything else?

 
 
 
 
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5 weeks ago, # |
  Vote: I like it +21 Vote: I do not like it

The audio is very understandable, great! For me, E was particularly relevant. Unfortunately, I didn't understand the math. The part could have been more detailed.

I understand that we are looking for components from fields of the same color, and the result depends on how many white fields are next to each other. The calculation of the result for a given number of neighboring white fields is still unclear to me.

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    5 weeks ago, # ^ |
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    Yeah. I was rushing to write the solution. I should've explained it in more detail maybe. I didn't understand what is it more about: solving problems or explaining the solutions.

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      5 weeks ago, # ^ |
        Vote: I like it +21 Vote: I do not like it

      When you decide who the target audience is, you can adjust the level of detail accordingly. Maybe the target audience has sligtly more math skills than me ;)

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      5 weeks ago, # ^ |
        Vote: I like it +18 Vote: I do not like it

      I think most of the larger youtubers do a post-contest analysis.

      But personally I watch these screencast to see how people think (what they noticed first, how they prune the solution space, etc). I don't really care for a detail explanation if that's not what you usually do. There are editorials for that.

      Side note: I really enjoyed your screencast btw! I didn't even find it because of this blog, it came up organically in my recommendations. Hope to see more!

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        5 weeks ago, # ^ |
          Vote: I like it +12 Vote: I do not like it

        Wow, yeah. You definitely got a point. It makes a lot of sense. Now I understand it better.

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4 weeks ago, # |
  Vote: I like it +10 Vote: I do not like it

From your youtube comment -
We want every substring of size two to appear the same (or pretty much the same) amount of times. It's well known that there's a string that contains all the substrings of size x exactly once. I construct this string for x=2 using the Euler cycle and then just repeat it.

How to do it for larger x?

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    4 weeks ago, # ^ |
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    Let's make vertices for all the substrings of size $$$x - 1$$$. And add edges 'a', 'b', ..., 'z' from every vertex (if we add this character to the end of the current string, what's the new suffix of length $$$x - 1$$$?). In this case, every vertex has its in-degree equal 26 and out-degree equal 26. So there's an Euler cycle in this graph. Here every edge represents a string of size $$$x$$$. So we can construct a string that consists of all the strings of size $$$x$$$ exactly once.

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      4 weeks ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Thanks! Now I also understand why the Euler cycle for the complete graph works. Because each edge has a substring of size x written on it. And Euler cycle writes out all edges exactly once, right?

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4 weeks ago, # |
  Vote: I like it +1 Vote: I do not like it

The screencast was amazing. Normally I don't watch the screencasts because there is hardly any explanation involved. But the way you think aloud while working things out on the board, is different from others imo (in a good way). Also, the audio clarity was superb.