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  1. #include <iostream>
  2.  
  3. unsigned long concatenateArr_Sone( unsigned* first, unsigned* last )
  4. {
  5.     unsigned long value = 0,
  6.                   ct = 1;
  7.  
  8.     while( last-- != first )
  9.     {
  10.         if( *last > 9 )
  11.         {
  12.             value += ct * (*last % 10);
  13.             *last++ /= 10;
  14.         }
  15.         else
  16.             value += ct * *last;
  17.  
  18.         ct *= 10;
  19.     }
  20.  
  21.     return value;
  22. }
  23.  
  24. unsigned append_number(unsigned x, unsigned y) {
  25.   return (y < 10 ? x : append_number(x, y / 10)) * 10 + y % 10;
  26. }
  27.  
  28. #include <numeric>
  29.  
  30. unsigned long concatenateArr_Seldon( unsigned* first, unsigned* last )
  31. {
  32.     return std::accumulate(first, last, 0ul, append_number);
  33. }
  34.  
  35. #include <iterator>
  36. #include <random>
  37. #include <algorithm>
  38. #include <iomanip>
  39. #include <chrono>
  40. #include <ctime>
  41.  
  42. unsigned arr[5];
  43.  
  44. template<typename Callable>
  45. void check( std::string const& name, Callable&& Foo )
  46. {
  47.     std::cout << '\n' << name << ": " << Foo( std::begin(arr), std::end(arr) ) << ", needed ";
  48.  
  49.     using namespace std::chrono;
  50.     auto _tp = system_clock::now();
  51.  
  52.     for( unsigned ct = 0; ct < 10000000; ++ct )
  53.         auto val = Foo( std::begin(arr), std::end(arr) );
  54.  
  55.     std::cout << (system_clock::now() - _tp).count() << " ticks";
  56. }
  57.  
  58. int main()
  59. {
  60.     std::uniform_int_distribution<unsigned> dist(0, 100);
  61.     std::minstd_rand device(time(nullptr));
  62.     std::generate( std::begin(arr), std::end(arr), std::bind(dist, device) );
  63.  
  64.     std::cout << "Values: ";
  65.     std::copy( std::begin(arr), std::end(arr), std::ostream_iterator<unsigned>(std::cout, ", ") );
  66.  
  67.     check( "Seldon", concatenateArr_Seldon );
  68.     check( "Sone  ", concatenateArr_Sone );
  69. }
Success #stdin #stdout 0.8s 2988KB
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Standard input is empty
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Values: 44, 56, 90, 59, 3, 
Seldon: 445690593, needed 648788 ticks
Sone  : 445690593, needed 154826 ticks
https://ideone.com/xaVu7H
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
secret

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