Traversing a tree - How to print the edges first

Question

If I have a tree as below:

          A                Root Level
        /   \
       /     \
      G       Z            Level 1
     / \     /  \
    /   \   /    \
   C     D  T     J        Level 2

I have three questions:

How can I traverse this tree such that Level 1 nodes are printed first, then root level, and then level 2

G, Z, A, C, D, T, J
How can I traverse this tree such that Level 1 nodes are printed first, then level 2, and then root level

G, Z, C, D, T, J, A
How can I traverse this tree such that Level 2 nodes are printed first, then level 1, and then root level

C, D, T, J, G, Z, A

I'm going through tree traverals on wikipedia and remembered an old question I was once asked in an interview. I believe the question was either of the above three (most likely first or second).

You may be interested in this: http://en.wikipedia.org/wiki/Breadth-first. — Oliver Charlesworth, Jun 10 '12 at 18:04

score 0 · Answer 1 · answered Jun 10 '12 at 21:21

Preorder traversal: visit root before the subtrees

void preorder( BTREE__NODE_p_t node )
    if ( node != NULL )
        visit( node )
        preorder( node->left )
        preorder( node->right )

Inorder traversal: visit root between visiting the subtrees

void inorder( BTREE__NODE_p_t node )
    if ( node != NULL )
        inorder( node->left )
        visit( node )
        inorder( node->right )

Postorder traversal: visit root after visiting the subtrees

void postorder( BTREE__NODE_p_t node )
    if ( node != NULL )
        postorder( node->left )
        postorder( node->right )
        visit( node )

just to be clear, do want the algorithm to be generic, something like applying to n levels or just 3, cause the difference is like huge in terms of logic.

Traversing a tree - How to print the edges first

1 Answers1