Traverse tree without recursion and stack in C

Question

How to traverse each node of a tree efficiently without recursion in C (no C++)?

Suppose I have the following node structure of that tree:

struct Node
{
         


        

Answer 1

This looks like an exercise I did in Engineering school 25 years ago. I think this is called the tree-envelope algorithm, since it plots the envelope of the tree.

I can't believe it is that simple. I must have made an oblivious mistake somewhere. Any mistake regardless, I believe the enveloping strategy is correct. If code is erroneous, just treat it as pseudo-code.

while current node exists{
  go down all the way until a leaf is reached;
  set current node = leaf node;
  visit the node (do whatever needs to be done with the node);

  get the next sibling to the current node;
  if no node next to the current{
    ascend the parentage trail until a higher parent has a next sibling;
  }
  set current node = found sibling node;
}

The code:

void traverse(Node* node){

  while(node!=null){
    while (node->child!=null){
      node = node->child;
    }

    visit(node);

    node = getNextParent(Node* node);
  }
}

/* ascend until reaches a non-null uncle or 
 * grand-uncle or ... grand-grand...uncle
 */
Node* getNextParent(Node* node){

  /* See if a next node exists
   * Otherwise, find a parentage node
   * that has a next node
   */
  while(node->next==null){
    node = node->parent;
    /* parent node is null means
     * tree traversal is completed
     */
    if (node==null)
      break;
  }

  node = node->next;

  return node;
}