number of nodes for a level in a first child - next sibling tree

Question

I have to write a function to find the number of nodes in a level of a first child - next sibling N-ary tree. My function is:

int nodesAtLevel(NTree root, int level) {
    if (root == NULL) {
        return 0;
    }
    if (level == 0) {
        return 1;
    }
    return nodesAtLevel(root->firstChild, level - 1) + 
           nodesAtLevel(root->nextSibling, level - 1);
}

but it does not work. Can someone help me?

Answer 1

Right now, your code seems to only return 2. I believe this is what you are trying to do:

int nodesAtLevel(NTree root, int level) {
    if (root == NULL) {
        return 0;
    }
    if (level == 0) {
        return 1;
    }

    int x = nodesAtLevel(root->firstChild, level - 1);
    int y = nodesAtLevel(root->nextSibling, level - 1);

    return x + y + 1; //add 1 for current node
}

This should update the value after every recursion, unlike your current code.