Question

I have something of the form:

struct Tree {
    string rule;
    list<Tree*> children;
}

I’m trying to print it out from within this for loop.

for(list<Tree*>::iterator it=(t->children).begin(); it != (t->children).end(); it++) {
    // print out here
}

Answer 1

You can always turn recursion into iteration. Here’s with an auxiliary queue:

std::deque<Tree *> todo;

todo.push_back(t);

while (!todo.empty())
{
    Tree * p = todo.front();
    todo.pop_front();

    std::cout << p->rule << std::endl;

    todo.insert(todo.end(), p->children.begin(), p->children.end());
}

In C++11 this would of course be a for loop:

for (std::deque<Tree *> todo { { t } }; !todo.empty(); )
{
    // ...
}