Function for BFS.

// Function for Breadth-First Search in CPP
// nodeptr = TreeNode*

void bfs(nodeptr first) {
    queue <nodeptr> i;
    if (first != NULL)
        i.push(first);
    while (!i.empty()) {
        if (i.front()->left != NULL)
            i.push(i.front()->left);
        if (i.front()->right != NULL)
            i.push(i.front()->right);
        cout << i.front()->key << " ";
        i.pop();
    }
    cout << endl;
}