Example 4: An example to illustrate differences between algorithms in Group #2,#3 and #4

typedef struct S {
        int data;
        S * next;
}S;

foo( S *x, S *y)
{
        x->next = y;
}

S st1, st2

main( )
{
        foo(&st1, &st1) /* call site C1 */
        .......
        foo(&st1, &st2) /* call site C2 */
}