public boolean isSumTree(Node root){
        Count count = new Count();
        return isSumTree(root,count);
    }
http://www.geeksforgeeks.org/check-if-a-given-binary-tree-is-sumtree/
A SumTree is a Binary Tree where the value of a node is equal to sum of the nodes present 
in its left subtree and right subtree
src/com/interview/tree/SumTree.java