===== Quick Sort =====

<code C++>
#include <iostream>
#include <time.h>

using namespace std;

const int N = 1000000;

int a [N]; 

inline void swap (int i, int k)
{
    int t = a [i];
    a [i] = a [k];
    a [k] = t;
}

void quickSort (int r, int s)
// setridit a[r], ..., a[s]
{
    int i = r;
    int k = s;

    int h = a [ (r+s)/2 ];

    while (i <= k) 
    {
        while (a[i] < h) i++;
        while (a[k] > h) k--;

        if (i <= k)
        {
            swap (i, k); // prohodit a[i] <-> a[k]
            i ++;
            k --;
        }
    }

    if (r < k) quickSort (r, k);
    if (i < s) quickSort (i, s);
}

int main ()
{
    srand (time (nullptr));
    for (int i = 0; i < N; i++)
        a [i] = (rand () % 1000) + 1000 * (rand () % 1000);

    /*
    for (int i = 0; i < N; i++)
        cout << a [i] << endl;
    cout << endl;
    */

    quickSort (0, N-1);

    bool ok = true;
    for (int i = 0; i < N; i++)
    {
        if (i > 0 && a [i-1] > a [i]) { ok = false; cout << "CHYBA "; }
        // cout << a [i] << endl;
    }

    if (ok)
        cout << "O.K." << endl;
}
</code>