I have implemented a method to do a preorder traversal of a tree, which is not a binary tree. Every parent node of this tree has an array of children, so this is the method I am using:
void preorderTraversal(TreeNode tree)
{
if (tree == null)
return;
System.out.print(tree.element + " ");
for(TreeNode child : tree.childern) // children is an Arraylist
{
preorderTraversal(child);
}
}
Sample of linking children nodes to parent "tnAA"
/* Creating Object of class tree*/
Tree tree = new Tree();
tree.setRoot(tnAA);
TreeNode root2 = tree.getRoot();
/* creating the links between nodes of Tree*/
ArrayList<TreeNode> AA_children = new ArrayList<TreeNode>();
AA_children.add(tnBB);
AA_children.add(tnCC);
AA_children.add(tnDD);
tnBB.parent=tnAA; tnCC.parent = tnAA; tnDD.parent = tnAA;
// Tree
// A
// / | \
// B C D
// /\ |
// E F G
But it only outputs the root node, what's wrong with this method?
Solution: linking children array to each parent : tnAA.setChildern(AA_childern);
You never add anything to any node's childern
list. You create an ArrayList called AA_childern
, but it is not connected to the tree, and the tree doesn't know or care that it exists. Those child nodes need to be added to tnAA.childern
.
PS The correct spelling is 'child re n'.
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