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  1. #include <iostream>
  2. #include <iterator>
  3. #include <algorithm>
  4. #include <numeric>
  5. #include <thread>
  6. #include <vector>
  7.  
  8.  
  9. std::size_t count_needle(int * first, int *const last,
  10.                          int const* needleFirst, int const* const needleLast) {
  11.    std::sort(first, last);
  12.  
  13.    std::size_t count = 0;
  14.    while (first != last && needleFirst != needleLast) {
  15.       if (*first == *needleFirst) {
  16.          ++count;
  17.          ++first;
  18.       } else if (*needleFirst < *first) {
  19.          ++needleFirst;
  20.       } else {
  21.       	++first;
  22.       }
  23.    }
  24.  
  25.    return count;
  26. }
  27.  
  28.  
  29. int main()
  30. {
  31.     int arrayFirst[] = { 11, 5, 2, 8, 4, 5, 2, 5, 7, 9, 12, 16, 17, 18, 20 };
  32.     int arraySecond[] = { 22, 5, 8, 3, 2, 9, 4, 3, 9, 10 };
  33.  
  34.     std::sort(std::begin(arraySecond), std::end(arraySecond));
  35.     auto const arraySecondEnd = std::unique(std::begin(arraySecond), std::end(arraySecond));
  36.  
  37.     auto const numThreads = std::thread::hardware_concurrency();
  38.     std::vector<std::thread> tasks;
  39.     tasks.reserve(numThreads);
  40.     std::vector<size_t> results(numThreads);
  41.  
  42.     auto const firstSize  = sizeof(arrayFirst) / sizeof(*arrayFirst); 
  43.     auto const firstStep = (firstSize + numThreads - 1) / numThreads;
  44.  
  45.     for (std::size_t i = 0; i != numThreads; ++i) {
  46.     	auto const firstBegin = arrayFirst + i * firstStep;
  47.     	auto const firstEnd   = arrayFirst + std::min((i + 1) * firstStep, firstSize);
  48.  
  49.     	std::thread task([=, &results] () {
  50.     		results[i] = count_needle(firstBegin, firstEnd, arraySecond, arraySecondEnd);
  51.     	});
  52.     	tasks.push_back(std::move(task));
  53.     }
  54.  
  55.     for (auto & task : tasks) {
  56.        task.join();
  57.     }
  58.  
  59.     auto const count = std::accumulate(std::begin(results), std::end(results), std::size_t(0));
  60.  
  61.     std::cout << count << std::endl;
  62. }
Success #stdin #stdout 0s 23456KB
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https://ideone.com/LTTluC
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
secret

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