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  1. // author Masaki Hara (qnighy)
  2. // Public Domain
  3. #include <cstdio>
  4. #include <iostream>
  5. using namespace std;
  6.  
  7. // for 64-bit environment, but works on 32bit too
  8. template<size_t N> struct roundUp {
  9.   // corner case: x=0, x>2^63
  10.   static const size_t _N1 = N-1;
  11.   static const size_t _N2 = _N1 | (_N1 >>  1);
  12.   static const size_t _N3 = _N2 | (_N2 >>  2);
  13.   static const size_t _N4 = _N3 | (_N3 >>  4);
  14.   static const size_t _N5 = _N4 | (_N4 >>  8);
  15.   static const size_t _N6 = _N5 | (_N5 >> 16);
  16.   static const size_t _N7 = _N6 | (_N6 >> 32);
  17.   static const size_t Value = _N7 + 1;
  18. };
  19.  
  20. int main() {
  21.   cout << roundUp< 1>::Value << endl;
  22.   cout << roundUp< 2>::Value << endl;
  23.   cout << roundUp< 3>::Value << endl;
  24.   cout << roundUp< 4>::Value << endl;
  25.   cout << roundUp< 5>::Value << endl;
  26.   cout << roundUp< 6>::Value << endl;
  27.   cout << roundUp< 7>::Value << endl;
  28.   cout << roundUp< 8>::Value << endl;
  29.   cout << roundUp< 9>::Value << endl;
  30.   cout << roundUp<10>::Value << endl;
  31.   return 0;
  32. }
  33.  
Success #stdin #stdout 0.01s 2724KB
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https://ideone.com/EStSRd
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
public

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