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Discussion of Problem 1996. Cipher Message 3andreyDagger`~ The most stupid Mistake ever. TL15 // Problem 1996. Cipher Message 3 23 Jun 2023 01:41 I spent 20 submissions, because of TLE15. I tried many fft implementations. But the error was in my z function Vedernikoff 'Goryinyich' Sergey (HSE: АОП) My implementation of FFT is not fast enough, or there is more simple solution to the problem? (-) [2] // Problem 1996. Cipher Message 3 10 Feb 2014 00:44 Edited by author 10.02.2014 00:44 IPRIT Re: My implementation of FFT is not fast enough, or there is more simple solution to the problem? (-) [1] // Problem 1996. Cipher Message 3 2 Aug 2014 17:58 Use the FFTW (such fast wow) for AC. Vedernikoff 'Goryinyich' Sergey (HSE: АОП) Re: My implementation of FFT is not fast enough, or there is more simple solution to the problem? (-) // Problem 1996. Cipher Message 3 4 Aug 2014 02:14 Thanks, I already got AC with usual FFT (heavily optimized). Could you give some link to FFTW? BUET_Bats Can't understand the first test case [2] // Problem 1996. Cipher Message 3 26 Oct 2013 15:33 3 2 11110001 11110001 11110000 11110000 11110000 If you alter one bit, it will become 11110000 11110000 11110001 So how the answer is 1 2? Shouldn't it be 1 1? Or we have to alter only the first byte? espr1t Re: Can't understand the first test case [1] // Problem 1996. Cipher Message 3 26 Oct 2013 17:29 What you suggest changes 2 bits and you want the replacement with minimal number of bits ("And if it is, find the minimum number of bits to alter."). Edited by author 26.10.2013 17:33 Edited by author 26.10.2013 17:36 IPRIT Re: Can't understand the first test case // Problem 1996. Cipher Message 3 2 Aug 2014 17:59 Use the FFTW. impetus What is the minimum number of bits? [3] // Problem 1996. Cipher Message 3 28 Oct 2013 20:12 I have 3 different understandings of the target value: 1. Whole number of bits in all bytes to be changed to make bit substrings equal (any bit(s) of each byte can be changed); 2. The same as p. 1, but only last consecutive bits of byte (suffix) can be changed; 3. The number from the 0..8 range which is the minimum number of bits that can be changed in all bytes. Tests do not clarify this. Which one is right? Kurpilyansky Eugene (USU) Re: What is the minimum number of bits? [2] // Problem 1996. Cipher Message 3 28 Oct 2013 21:29 It's allowed to change only last bit in every byte. impetus Re: What is the minimum number of bits? [1] // Problem 1996. Cipher Message 3 29 Oct 2013 00:48 OK)), thanks! IPRIT Re: What is the minimum number of bits? // Problem 1996. Cipher Message 3 2 Aug 2014 17:59 Use the FFTW. hehaodele does the order of the secret information files can be changed? [1] // Problem 1996. Cipher Message 3 27 Jun 2014 07:44 image: 00000010 00000001 secret: 00000000 00000011 can they match? IPRIT Re: does the order of the secret information files can be changed? // Problem 1996. Cipher Message 3 2 Aug 2014 17:58 Use the FFTW for AC. Edited by author 02.08.2014 17:59
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