Recursion example:Quicksort

/*qsort: sort v[left]....v[right] into increasing order */
void qsort(int v[], int left, int right){
     int i, last;
     void swap(int v[], int i , int j);
     
     if (left >= right)   /*do nothing if array contains */
         return;          /*fewer than two elements */
     swap(v, left, (left + right) /2);     /*move partition elem */
     last = left;                          /* to v[0] */
     for(i =left + 1; i <= right; i++)     /* partition */
         if (v[i] < v[left])
             swap(v, ++last, i);
     swap(v ,left, last);                /*restore partition elem */
     qsort(v ,left, last -1);
     qsort(v ,last + 1, right);
}