C2

C2.cpp

@@ -0,0 +1,57 @@
+#include <iostream>
+
+int QuickSelect(int* buffer, int n, int k) {
+  if (n == 1) {
+    return buffer[0];
+  }
+  int pivot = buffer[n/2];
+  int one_size = 0;
+  int two_size = 0;
+  for (int i = 0; i < n; i++) {
+    if (buffer[i] < pivot) {
+      one_size++;
+    }
+    if (buffer[i] > pivot) {
+      two_size++;
+    }
+  }
+  if (k < one_size) {
+    //delete[] two_arr ;
+    int* new_buffer = new int[one_size]; int cnt = 0;
+    for (int i = 0; i < n; i++){
+      if (buffer[i] < pivot){
+        new_buffer[cnt] = buffer[i]; cnt++;
+      }
+    }
+    QuickSelect(new_buffer, one_size, k);
+  }
+  else {
+    if (k >= one_size and k < n - two_size) {
+      return pivot;
+    }
+    else {
+      int* new_buffer = new int[two_size]; int cnt = 0;
+      for (int i = 0; i < n; i++){
+        if (buffer[i] > pivot){
+          new_buffer[cnt] = buffer[i]; cnt++;
+        }
+      }
+      QuickSelect(new_buffer, two_size, k - n + two_size);
+    }
+  }
+}
+
+int main() {
+  std::ios_base::sync_with_stdio(false);
+  std::cin.tie(NULL);
+  int n;
+  std::cin >> n;
+  int k;
+  std::cin >> k;
+  int* buffer = new int[n];
+  for (int i = 0; i < n; i++) {
+    std::cin >> buffer[i];
+  }
+  std::cout << QuickSelect(buffer, n, k);
+  delete[] buffer;
+}