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  1. #include <algorithm>
  2. #include <cmath>
  3. #include <iomanip>
  4. #include <iostream>
  5. #include <iterator>
  6. #include <numeric>
  7. #include <vector>
  8.  
  9. namespace detail {
  10. template <typename ForwardIterator>
  11. auto mean(ForwardIterator first, ForwardIterator last,
  12.           const std::size_t elements_count) {
  13.   const auto sum_of_elements = std::accumulate(first, last, 0.0);
  14.   return sum_of_elements / elements_count;
  15. }
  16.  
  17. template <typename ForwardIterator>
  18. auto variance(ForwardIterator first, ForwardIterator last,
  19.               const double elements_mean) {
  20.   auto VarianceAccumulator = [elements_mean](auto total, auto next_value) {
  21.     const auto diff = next_value - elements_mean;
  22.     return total + (diff * diff);
  23.   };
  24.  
  25.   return std::accumulate(first, last, 0.0, VarianceAccumulator);
  26. }
  27. } //namespace
  28.  
  29. template <typename ForwardIterator>
  30. auto mean(ForwardIterator first, ForwardIterator last) {
  31.   const auto element_count = std::distance(first, last);
  32.   return detail::mean(first, last, element_count);
  33. }
  34.  
  35. template <typename ForwardIterator>
  36. auto standard_deviation(ForwardIterator first, ForwardIterator last) {
  37.   const auto elements_count = std::distance(first, last);
  38.   const auto elements_mean = detail::mean(first, last, elements_count);
  39.   const auto elements_variance = detail::variance(first, last, elements_mean);
  40.  
  41.   return std::sqrt(elements_variance / elements_count);
  42. }
  43.  
  44. template <typename ForwardIterator>
  45. void print_standard_deviation(ForwardIterator first, ForwardIterator last,
  46.                               std::ostream &out) {
  47.   std::copy(first, last, std::ostream_iterator<int>(out, " "));
  48.   out << "\nStandard Deviation: " << std::setprecision(4) << std::fixed
  49.       << standard_deviation(first, last) << '\n' << '\n';
  50. }
  51.  
  52. int main() {
  53.   std::vector<std::vector<int>> inputs{
  54.       {5, 6, 11, 13, 19, 20, 25, 26, 28, 37},
  55.       {37, 81, 86, 91, 97, 108, 109, 112, 112, 114, 115, 117, 121, 123, 141},
  56.       {266, 344, 375, 399, 409, 433, 436, 440, 449, 476, 502, 504, 530, 584,
  57.        587},
  58.       {809, 816, 833, 849, 851, 961, 976, 1009, 1069, 1125, 1161, 1172, 1178,
  59.        1187, 1208, 1215, 1229, 1241, 1260, 1373}};
  60.  
  61.   for (const auto &input : inputs) {
  62.     print_standard_deviation(input.begin(), input.end(), std::cout);
  63.   }
  64. }
Success #stdin #stdout 0s 3276KB
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stdin
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Standard input is empty
stdout
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5 6 11 13 19 20 25 26 28 37 
Standard Deviation: 9.7775

37 81 86 91 97 108 109 112 112 114 115 117 121 123 141 
Standard Deviation: 23.2908

266 344 375 399 409 433 436 440 449 476 502 504 530 584 587 
Standard Deviation: 83.6616

809 816 833 849 851 961 976 1009 1069 1125 1161 1172 1178 1187 1208 1215 1229 1241 1260 1373 
Standard Deviation: 170.1273
https://ideone.com/BbxaiB
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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