dead-loop in depth-first-search

[noodles-v6]

I found the duplication state might be happen at

void simulation::depth_first_search(state* initial)
 ...
                if (s->board()->areas()->pop(&a)) {
        if (a->size() < 3) {
            delete a;
            continue;
        }

        state* p = new state(s, *a);
        GRAPH(s, &a->point(), p);
        stack.push(p);
        delete a;
        continue;
    }

I think you should check the new state whether or not duplication before stack.push(p).
if duplication, skip.