Binary Tree Order Traversal

Question | May 23, 2016 | rparekh 

Below is a binary tree with elements:

enter image description here

The tree, 'Tree' and its node 'Node' are represented as:

struct Node {
    std::string key;
    Node* left;
    Node* right;
    Node(std::string& k)
       :key(k),left(NULL),right(NULL) {}
};

struct Tree {
    Tree():root(NULL){}
    void traversal(Node* n);
    // .... more methods......
    Node* root;
};

What is the correct algorithm to travel the tree in the following sequence of the nodes?

A A B E F G  
2015 nextptr