quicksort experiments

task2/include/quicksort_mt.h

@@ -36,7 +36,7 @@ private:
             std::swap(*lefti, *righti);
         }
 
-        return {std::span<T>(data.begin(), pivot - 1), std::span<T>(pivot + 1, data.end())};
+        return {std::span<T>(data.begin(), pivot), std::span<T>(pivot, data.end())};
     }
 
 
@@ -50,9 +50,18 @@ private:
             }
         }
 
-        auto res = parition(data);
-        auto &left = res.first;
-        auto &right = res.second;
+        auto pivot = data[std::distance(data.begin(), data.end()) / 2];
+
+        auto m1 = std::partition(data.begin(), data.end(), [pivot, this](const auto &em) {
+            return this->cmp(em, pivot);
+        });
+
+        auto m2 = std::partition(m1, data.end(), [pivot, this](const auto &em) {
+            return !(this->cmp(em, pivot));
+        });
+
+        auto left = data.subspan(0, m1 - data.begin());
+        auto right = data.subspan(m2 - data.begin(), data.size());
 
         if (depth < mdepth) {
             std::thread left_thread([&]() { qsort(left, depth + 1, mdepth); });