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2/B.cpp

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+#include <iostream>
+#include <cstdlib>
+#include <ctime>
+
+int Partition(int* arr, int start, int end);
+void PrintArray(int* arr, int start, int end);
+void QuickSort(int* arr, int start, int end);
+
+void PrintArray(int* arr, int start, int end) {
+  for (int i = start; i <= end; ++i) {
+    std::cout << arr[i] << " ";
+  }
+  std::cout << "\n";
+}
+
+int Partition(int* arr, int start, int end) {
+  int pivot = arr[std::rand() % (end - start + 1) + start];
+  int i = start - 1;
+  int j = end + 1;
+
+  // move pivot to the start
+  while (true) {
+    do {
+      ++i;
+    } while (arr[i] < pivot);
+
+    do {
+      --j;
+    } while (arr[j] > pivot);
+
+    if (i >= j)
+      return j;
+
+    std::swap(arr[i], arr[j]);
+  }
+}
+
+void QuickSort(int* arr, int start, int end) { // NOLINT(*-no-recursion)
+  if (start >= end)
+    return;
+
+  int pivot_idx = Partition(arr, start, end);
+
+  QuickSort(arr, start, pivot_idx);
+  QuickSort(arr, pivot_idx + 1, end);
+
+}
+
+int main() {
+  int size;
+  std::cin >> size;
+  int* a = new int[size];
+
+  for (int i = 0; i < size; ++i) {
+    std::cin >> a[i];
+  }
+
+  std::srand(std::time(nullptr));
+  QuickSort(a, 0, size - 1);
+  PrintArray(a, 0, size - 1);
+
+  delete[] a;
+
+  return 0;
+}