Binary Tree nodes and relations to the parent [duplicate] - c

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C How to "draw" a Binary Tree to the console [closed]
(10 answers)
Closed 3 years ago.
I know how to code a binary search tree, and to traverse it in inorder, preorder or postorder fashion.
But, I want to know how I can know where the actual node is:
For example let's say we have the values: 70 90 50 60 80 40
So the root would be 70, 90 to its right, 50 to its left, 60 to 50's right and so on.
So if I were to print this inorder, it would be 40 50 60 70 80 90, increasing order pretty much.
I do this by doing this in the recursive traverse function:
traverse(root->left);
printf("%d ", root->data);
traverse(root->right);
But this doesn't let me know (as far as I know) where the node currently is.
Is there a way to print the tree like this?:
70
50 (70 L) 90 (70 R) // We know which parent the node is from and we know if it's the left or the right of it.
40 (50 L) 60 (50 R) 80 (90 L)
and so on.. if the tree is bigger.
I don't really know how I'd do it. Would I need to link them to their parents? But how would I know the right-left thing if I do just that? Or do I need to print the child when the iterator is on the parent still. Thank you in advance.
Edit: I looked up printing the tree by traversing level by level but I don't think I get to know the parent and the side of the node.. I am trying to implement some codes to c code and I always get crashes.

Answer 1

Seems you want to print the tree level by level, i.e.
level 0: node0
level 1: node1 (node0 L) node2 (node0 R)
level 2: ...
So you need a way to track the current level and the target level (i.e. the one you want to print). Also you need a way to track when there is "no more levels" (i.e. no more to print).
That can be done in many ways. The pseudo code below should give you an idea of one way to do it. It's not the most efficient way but it's pretty simple.
Something like:
bool btPrintLevel(node* root, int targetlevel, int currentlevel)
{
if (targetlevel == currentlevel) return false; // no need to go further down in levels
bool result = false;
result |= btPrintLevel(root->left, targetlevel, currentlevel + 1);
// psedo code
if ((currentlevel + 1 == targetlevel)
{
if (childern_exists)
{
printChildern(...)
result = true;
}
}
result |= btPrintLevel(root->right, targetlevel, currentlevel + 1);
return result;
}
Called like:
int level = 0;
while(btPrintLevel(head, level)) ++level;
This How to print elements from Binary Tree by level in c may also help. It doesn't do exactly what you want but with minor modifications you can achieve your goal.

Answer 2

Recursive algorithms are fine for depth-first traversing of trees, but less suitable for broadth-first. The latter can be done pretty efficiently using a FIFO (pseudo code):
push(fifo, { root, 0 });
while(!isEmpty(fifo))
{
node* n = pop(fifo);
print(n);
if(n->left)
push(fifo, { n->left, 'L' });
if(n->right)
push(fifo, { n->right, 'R'});
}
I've foreseen an additional field designating being left or right child of parent. If you your nodes have a link to their parent, you can instead decide upon n->parent->left == n ? 'L' : 'R'.
Leaving implementing the FIFO up to you (you'll find quite a number of questions here on SO about)...