package problems.medium;
import problems.utils.TreeNode;
/**
* Created by sherxon on 3/19/17.
*/
public class ConvertBSTToGreaterTree {
public TreeNode convertBST(TreeNode root) {
if (root == null) return null;
f(root, 0);
return root;
}
int f(TreeNode root, int val) {
if (root == null) return val;
int r = f(root.right, val);
root.val = r + root.val;
return f(root.left, root.val);
}
}