Question

From Programming Pearls: Column 12: Searching:
There are two code segments:

    IntSetList(int maxelements, int maxval)
    {   sentinel = head = new node(maxval, 0);
        n = 0;
    }
    void report(int *v)
    {   int j = 0;
        for (node *p = head; p != sentinel; p = p->next)
            v[j++] = p->val;
    }

I’m curious how does the sentinel work in the report function?

If necessary, please see the complete source code.

Thanks,

Answer 1

sentinel is just the value that the last pointer in the list is expected to have; it’s the value that a next member has when it doesn’t point to anything. It’s initialized to point to the first, “dummy” node in the list; new items are inserted at the beginning, so the sentinel drifts to the end.