void quick_sort(int *ptr, int left, int right) {
int i, j;
if(left >= right) return;
j = left;
for(i=left+1; i <= right; i++)
if(*(ptr+i) < *(ptr+left))
swap(ptr+(++j), ptr+i);
swap(ptr+left, ptr+j);
quick_sort(ptr, left, j-1);
quick_sort(ptr, j+1, right);
}

void swap(int *ptr1, int *ptr2) {
int w;
w = *ptr1;
*ptr1 = *ptr2;
*ptr2 = w;
}