import std.stdio, std.algorithm;

void quickSort(ref int[] arr) {
  if (arr.length == 1) return;

  int wall = 0;
  int pivot = arr[$-1];

  foreach (a; 1..arr.length-1) {
    if (arr[a] <= pivot) {
      swap(arr[wall], arr[a]);
      wall++;
    }
  }

  swap(arr[wall+1], arr[$-1]);

  quickSort(arr[0..wall]);
  quickSort(arr[wall+1..$]);
}

void main() {
  int[] test = [6, 5, 1, 3, 8, 4, 7, 9, 2];
  quickSort(test);
  writeln(test);
}