Add zip-sort-unzip version of quicksort with permutations.

BaseLib/quicksort.h

@@ -111,6 +111,35 @@ void quicksort(T1* array, std::size_t beg, std::size_t end, T2* second_array)
 
 namespace BaseLib
 {
+
+template <typename T1, typename T2 = std::size_t>
+void quicksortD(std::vector<T1>& array, std::size_t beg, std::size_t end, std::vector<T2>& perm)
+{
+	// Zip input arrays.
+	std::vector<std::pair<T1, T2>> data;
+	data.reserve(array.size());
+	std::transform(array.begin(), array.end(), perm.begin(),
+		std::back_inserter(data),
+		[](T1 const& t1, T2 const& t2)
+		{
+			return std::make_pair(t1, t2);
+		});
+
+	// Sort data using first element of the pair.
+	std::sort(data.begin(), data.end(),
+		[](std::pair<T1, T2> const& a, std::pair<T1, T2> const& b)
+		{
+			return (a.first < b.first);
+		});
+
+	// Unzip sorted data.
+	for (std::size_t i = 0; i < data.size(); i++)
+	{
+		array[i] = data[i].first;
+		perm[i] = data[i].second;
+	}
+}
+
 template <typename T1, typename T2 = std::size_t>
 class Quicksort
 {