upload

2/I.cpp

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+#include <iostream>
+#include <cstdlib>
+#include <ctime>
+
+int OrderStatistic(int32_t* arr, int size, int k);
+int Partition(int32_t* arr, int start, int end);
+
+int Partition(int32_t* arr, int start, int end) {
+  int32_t pivot = arr[std::rand() % (end - start + 1) + start];
+  int i = start - 1;
+  int j = end + 1;
+
+  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]);
+  }
+}
+
+int OrderStatistic(int32_t* arr, int size, int k) {
+  int left = 0;
+  int right = size - 1;
+
+  while (true) {
+    int mid = Partition(arr, left, right);
+
+    if (mid == k) {
+      return arr[mid];
+    } else if (k < mid) {
+      right = mid;
+    } else {
+      left = mid + 1;
+    }
+  }
+}
+
+int main() {
+  std::srand(std::time(nullptr));
+
+  int n, k, A, B, C;
+  std::cin >> n >> k >> A >> B >> C;
+  int32_t* a = new int32_t[n];
+  std::cin >> a[0] >> a[1];
+
+  for (int i = 2; i < n; ++i) {
+    a[i] = a[i-2]*A + a[i-1]*B + C;
+  }
+
+  OrderStatistic(a, n, k - 1);
+
+  int32_t out = 0;
+  for (int i = 0; i < k; ++i) {
+    out ^= a[i];
+  }
+
+  std::cout << out;
+
+  delete[] a;
+  return 0;
+}