Files
concurrency-in-action/ch4/quicksort.cpp
2018-10-18 00:40:34 -05:00

71 lines
1.9 KiB
C++

#include <algorithm>
#include <cstdio>
#include <future>
#include <iostream>
#include <list>
#include <memory>
#include <thread>
std::ostream&
operator<<(std::ostream& ostr, const std::list<int>& list)
{
for (auto& i : list) {
ostr << " " << i;
}
return ostr;
}
template <typename T>
std::list<T>
sequential_quick_sort(std::list<T> input)
{
if (input.empty()) {
return input;
}
std::list<T> result;
result.splice(result.begin(), input, input.begin());
T const& pivot = *result.begin();
auto divide_point = std::partition(
input.begin(), input.end(), [&](T const& t) { return t < pivot; });
std::list<T> lower_part;
lower_part.splice(lower_part.end(), input, input.begin(), divide_point);
auto new_lower(sequential_quick_sort(std::move(lower_part)));
auto new_higher(sequential_quick_sort(std::move(input)));
result.splice(result.end(), new_higher);
result.splice(result.begin(), new_lower);
return result;
}
template <typename T>
std::list<T>
parallel_quick_sort(std::list<T> input)
{
if (input.empty()) {
return input;
}
std::list<T> result;
result.splice(result.begin(), input, input.begin());
T const& pivot = *result.begin();
auto divide_point = std::partition(
input.begin(), input.end(), [&](T const& t) { return t < pivot; });
std::list<T> lower_part;
lower_part.splice(lower_part.end(), input, input.begin(), divide_point);
std::future<std::list<T>> new_lower(
std::async(&parallel_quick_sort<T>, std::move(lower_part)));
auto new_higher(parallel_quick_sort(std::move(input)));
result.splice(result.end(), new_higher);
result.splice(result.begin(), new_lower.get());
return result;
}
int
main()
{
std::list<int> list1 = {4, 2, 1, 5, 8, 9, 7};
std::list<int> sorted1 = sequential_quick_sort(list1);
std::list<int> sorted2 = parallel_quick_sort(list1);
std::cout << "sorted1: " << sorted1 << std::endl;
std::cout << "sorted2: " << sorted2 << std::endl;
return 0;
}