In pre-order traversal, each node is processed before (pre) either of it's sub-trees. This is the simplest traversal to understand. However, even though each node is processed before the subtrees, it still requires that some information must be maintained while moving down the tree.
Preorder traversal is defined as follows:
- Visit the root.
- Traverse the left subtree in Preorder.
- Traverse the right subtree in Preorder.
Java code for above implement is as below:
package askgif.tree;
class Node
{
int data;
Node left, right;
public Node(int item)
{
data = item;
left = right = null;
}
}
class BinaryTree
{
Node root;
BinaryTree()
{
root = null;
}
}
public class TreeQuestions {
public static void main(String[] args) {
BinaryTree binaryTree = new BinaryTree();
Node root = new Node(1);
binaryTree.root = root;
binaryTree.root.left = new Node(2);
binaryTree.root.right = new Node(3);
binaryTree.root.left.left = new Node(4);
binaryTree.root.left.right = new Node(5);
PrintPreOrderTraversal(root);
}
private static void PrintPreOrderTraversal(Node treeNode) {
if(treeNode == null)
return;
System.out.println(treeNode.data);
PrintPreOrderTraversal(treeNode.left);
PrintPreOrderTraversal(treeNode.right);
}
}
output:
1
2
4
5
3
