[GeeksForGeeks] Write a program to delete a tree

Write a program to delete a tree.

Solution. 

To delete all tree nodes, we need to set all non-leaf nodes' children nodes to null. So for a given non-leaf node, 

set its left child node to null, then set its right child node to null, then set the reference of this node to null. 

This manifests a post order traversal of a given binary tree. 

public class DeleteTree {
    public void deleteTree(TreeNode node) {
        if(node == null) {
            return;
        }
        deleteTree(node.left);
        deleteTree(node.right);
        node = null;
    }
}

Follow up question: Can you solve this problem without using recursion?