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  1. #include <string>
  2. #include <iostream>
  3.  
  4. std::size_t preceding_pow2(std::size_t v)
  5. {
  6.     v--;
  7.     v |= v >> 1;
  8.     v |= v >> 2;
  9.     v |= v >> 4;
  10.     v |= v >> 8;
  11.     v |= v >> 16;
  12.     return (++v) >> 1;
  13. }
  14.  
  15. int main(int argc, char* argv[])
  16. {
  17.     std::size_t n = argc > 1 ? std::stoull(argv[1]) : 1ULL << 6;
  18.     for (std::size_t i = 0; i < n; ++i) {
  19.         std::cout << i << " " << preceding_pow2(i) << std::endl;
  20.     }
  21.     return 0;
  22. }
  23.  
Success #stdin #stdout 0s 16064KB
comments (?)
stdin
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Standard input is empty
stdout
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0 0
1 0
2 1
3 2
4 2
5 4
6 4
7 4
8 4
9 8
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12 8
13 8
14 8
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https://ideone.com/mZT13I
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
public

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