BT16.java

public class BT16 {

    static class Node {

        int data;
        Node right;
        Node left;

        Node(int data) {
            this.data = data;
            this.left = null;
            this.right = null;
        }
    }

    static int TransformToSum(Node root) {
        if (root == null) {
            return 0;
        }
        int ld = TransformToSum(root.left);
        int rd = TransformToSum(root.right);
        int newleft = root.left == null ? 0 : root.left.data;
        int newright = root.right == null ? 0 : root.right.data;
        int data = root.data;

        root.data = newleft + newright + ld + rd;
        return data;

    }

    public static void main(String[] args) {

        Node root = new Node(1);
        root.left = new Node(2);
        root.right = new Node(3);
        root.left.left = new Node(4);
        root.left.right = new Node(5);
        root.right.left = new Node(6);
        root.right.right = new Node(7);
        TransformToSum(root);

        System.out.println(root.data);
        System.out.println(root.left.data);
        System.out.println(root.right.data);
        System.out.println(root.left.left.data);

    }

}