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void quickSort(int a[], int l, int r)
{
int p = a[(l + r) / 2];
int i = l, j = r;
while (i < j)
{
while (a[i] < p)
{
i++;
}
while (a[j] > p)
{
j--;
}
if (i <= j)
{
int temp = a[i];
a[i] = a[j];
a[j] = temp;
i++;
j--;
}
}
if (i < r)
{
quickSort(a, i, r);
}
if (l < j)
{
quickSort(a, l, j);
}
}