chapter 4 code

ch4/quicksort.cpp

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+#include <iostream>
+#include <cstdio>
+#include <list>
+#include <thread>
+#include <memory>
+#include <algorithm>
+#include <future>
+
+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;
+}
+