Transform_to_sum_tree

int helper(Node* node)
    {
        int x,y,sum=0;
        if(node)
        {
            x=helper(node->left);
            y=helper(node->right);
            sum=node->data+x+y;
            node->data=x+y;
            return sum;
        }
        else
        return 0;
    }
    void toSumTree(Node *node)
    {
        helper(node);
    }