Friendpaste

#include <iostream>
#include <vector>

using namespace std;

void swap(int &a, int &b)
{
     int temp;
     a = b;
     b = temp;
}

int split_array(vector<int>& array, int pivot, int start_index, int end_index)
{
     int left_boundary = start_index;
     int right_boundary = end_index;

     while (left_boundary < right_boundary) {
	  while (pivot < array[right_boundary] && right_boundary > left_boundary) {
	       right_boundary--;
	  }

	  swap(array[left_boundary], array[right_boundary]);

	  while (pivot >= array[left_boundary] && left_boundary < right_boundary) {
	       left_boundary++;
	  }

	  swap(array[right_boundary], array[left_boundary]);
     }

     return left_boundary;
}

void quicksort(vector<int>& array, int start_index, int end_index)
{
     int pivot = array[start_index];
     int split_point;
     
     if (end_index > start_index) {
	  split_point = split_array(array, pivot, start_index, end_index);
	  array[split_point] = pivot;
	  quicksort(array, start_index, split_point-1);
	  quicksort(array, split_point+1, end_index);
     }
}