July 2022
[url]https://research.ibm.com/haifa/ponderthis/challenges/July2022.html[/url]

Shouldnâ€™t the last configuration in the example be (0, 8, 7) rather than (0, 7, 8)?

[QUOTE=a1call;608803]Shouldnâ€™t the last configuration in the example be (0, 8, 7) rather than (0, 7, 8)?[/QUOTE]
No, because after any operation, the sequence is reordered. 
I see. I missed reading the sorted in the following statement:
[CODE] Since we keep the cells in [B]sorted[/B] order, [/CODE] Thanks. 
I haven't done the bonus challenge yet, but the main challenge I solved in under an hour with no programming once I decided to actually work on it. I'm not sure if they intended it to be this easy.

A couple of clarifying questions for the bonus part:
 are people interpreting it as meaning you add the same value k, 1 <= k <= 30000000, to each cell?  my interpretation from the wording is that the sequence for the bonus question can be longer than 20 moves  do other people see it that way also? 
Seems like the bonus question would be impossible to solve the way I first interpreted it  the sum of the numbers is odd, and there are 10 numbers, so if you add the same value to each cell you will still have an odd number, and therefore it would be impossible to reduce from 2 nonzero cells to 1, since before the final move the 2 remaining cells would have to have equal value.
So how else am I meant to interpret adding up to 30M to the cells? Add whatever values I like to each cell provided the total amount added is <= 30M? 
[QUOTE]So how else am I meant to interpret adding up to 30M to the cells? Add whatever values I like to each cell provided the total amount added is <= 30M?[/QUOTE]
That's how I interpreted it, and the only requirement is that the result is solvable, no limit on number of moves required. The fact that they give you up to 30M to play with is a big clue to one possible solution (actually a set of solutions). But I found solutions that used much smaller amounts. I didn't write any code to search for solutions, and was able to solve both the main challenge and the bonus challenge very quickly. I don't think the main challenge was supposed to be as easy as I found it to be. 
Yeah, I can't see any other way to read the bonus question, but that interpretation does seem to make the bonus pretty easy (a good deal easier than the main question in my view). I didn't find the main question quite as trivial as you did, it took me a few hours. I solved it in two stages, with the first stage using code and the second by hand.

To make the bonus challenge more interesting, they should have given a much smaller amount to play with. I came up with a solution that adds less than 30K total to the cells, and there may be solutions using a smaller total amount than I came up with.

I think the number of steps was limited for the bonus question, too. But I see that the above discussions assumed that it is unlimited. I wonder if "at most 20 moves" is also enforced for the bonus part by the puzzlemaster.

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