[Community Puzzle] Solid Integer

Coding Games and Programming Challenges to Code Better

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Created by @Meepophobia,validated by @pardouin,@TimberStalker and @ChuOkupai.
If you have any issues, feel free to ping them.

I have solved the 4th first puzzles, but I can’t success for the last one (05 - Out of Memory).
If the 4th one were not correct, I would keep on searching, but it is.
Is the Expected output correct for puzzle 5? it’s expected 33646585979948395414, and I find 33646586081048405414 , which is weirdly close enough.
Thank you for your help?

Yes, the expected output is correct.

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Thank you!
:y bad actually, I have just noticed that my answer was involving … a 0 :rofl:

The correct solution of puzzle 5 is 33646586081048405414 not
33646585979948395414. The algorithm consists in writing n in base 9 and the solution x is equal to writing x in base 10 with the coefficients of n in base 9.

[don’t share your code here, please]

Your solution as 0 in it so it cannot be correct.

Also, you’re not supposed to give detailed explanation of how to solve the puzzle, let alone share your program.

my solution is mathematically correct.

A solid integer is an integer without 0. Yours has 0 i it, so it doesn’t work. I agree that it has to do with base 9 and your solution is close but you must slightly tweak your algorithm.

Cute puzzle. Very easy to solve once you realize the trick.

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and I don’t have the trick, can you help me ? x)

Think about how many solid integers there are for 1-digit numbers.
Then for 2-digit numbers.
Then for 3-digit numbers.
Work out a pattern.


I think some relevant tests are missing.
I posted a wrong solution that passed all the tests, but my answer would be wrong when the base 9 expression of n contains consecutive 0s.

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Are you able to access the contribution? You may leave a comment there to suggest what specific numbers to add as additional test cases and validators.

I don’t know how to access the contribution. The specific test case to add would be a value of n whose expression in base 9 has two or more consecutive 0s, like 81.

I agree. Looking through the solutions I think most will fail to print 9 as a 9th solid int.

Not far from the solution :wink:

Yes you’re right. I have to modify my code ! Thx

Hi, I technically solved the challenge by validating all the test cases (don’t get me wrong, I didn’t do a simple switch case) but I didn’t understand how to properly solve the underlying maths problem, if anyone is willing to share hints with me it would free my mind :’)

Spent more than 4 hours to finally solve it fully. It was a tough one for me.
Used two different techniques (wrt C++):

  1. (From pattern) base 9 conversion of n (dropped it since the the solid numbers containing 9 part was tricky to correct)
  2. Figure out how much to add in n, to find nth solid number (used string addition as the sum goes beyond unsigned long long) - AC