Cody

Rafael S.T. Vieira

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Rafael S.T. Vieira submitted a Comment to Problem 1701. Solve the picross! (Hard)

Solving a grid of 75x60 squares within Cody's time limit is extra hard. The greatest challenge is to find a fast code; recursion with backtracking no longer seems like a viable option. And I do hope the author is aware that nonograms are a NP-hard problem, which means there is no known fast algorithm to solve them: we have to build one for the specific cases of the test suite.

4 hours and 31 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 1700. Solve the picross! (Easy)

Nope, it's not easy. A grid of 20x20 squares is already considered hard by regular players because we have to keep in mind several possible intersections between possible solutions.

4 hours and 45 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 46943. Cipher the number

I am not sure this method can be called a cipher since there is probably no way to recover the original number. You should probably call it a hash.

10 hours and 14 minutes ago

Rafael S.T. Vieira submitted Solution 3409743 to Problem 46943. Cipher the number

10 hours and 32 minutes ago

Rafael S.T. Vieira submitted Solution 3409718 to Problem 46943. Cipher the number

10 hours and 33 minutes ago

Rafael S.T. Vieira liked Problem 47088. Function Call Counter

12 hours and 13 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 44971. Convert base 10 to base x (2-16)

Oh, the problem was with my algorithm, sorry. I am indeed using python's long int (for multiplication of large integers), but I was relying on str2num for some operations (which apparently introduced floats back in my code). After removing it, it worked out fine. PS: This new update knocked out some wrong solutions (including some of mine). Awesome. :)

on 26 Oct 2020 at 5:55

Rafael S.T. Vieira submitted a Comment to Problem 44964. Optimal Asymmetric Encryption Padding of message for RSA Cryptography

Thanks, David. I've struggled for a while with this problem but I've finally figured it out. First, although we don't use the encryption function from 7.1.1, we must create an output EM of length k-1 and apply a pad of 0 as the first character of EM (It was strange to see all hashes starting with 0). Next, I was confused with the Feistel Network, because my MGF from the previous problem wasn't working (an accepted solution), but I realized that you were probably using a hex input, instead of char (which is weird since the MGF function requires an Octect String as input), but anyway that solved it. :)

on 26 Oct 2020 at 5:46

Rafael S.T. Vieira submitted a Comment to Problem 2451. BLOCK x3 (Version 1)

https://noodlecake.com/games/blockblockblock/ (The game is no longer available at Google Play).

on 26 Oct 2020 at 3:11

Rafael S.T. Vieira submitted a Comment to Problem 1015. Polynomial Interpolation

FYI: The condition number of the Vandermonde coefficient matrix is just the norm of the matrix times the norm of its inverse. Cheers. PS: Wikipedia will just lead you to a paid wall. Don't waste time.

on 26 Oct 2020 at 2:47

Rafael S.T. Vieira submitted a Comment to Problem 44971. Convert base 10 to base x (2-16)

It seems the precision issues were indeed fixed. :)

on 25 Oct 2020 at 21:41

Rafael S.T. Vieira liked Problem 45362. RIPEMD160 Hash

on 25 Oct 2020 at 15:39

Rafael S.T. Vieira submitted a Comment to Problem 45320. SHA256 Hashing

The hardest thing is to use a hexadecimal input. Most on-line sites deal only with text. Exception: https://emn178.github.io/online-tools/sha256.html

on 25 Oct 2020 at 8:26

Rafael S.T. Vieira liked Problem 45320. SHA256 Hashing

on 25 Oct 2020 at 8:24

Rafael S.T. Vieira liked Problem 45347. Cat's paw - 01

on 25 Oct 2020 at 5:13

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