public boolean isSameTree(TreeNode p, TreeNode q) {
    	if (p == null && q == null)
    		return true;
        if(p == null && q !=null)
        	return false;
        if(p != null && q ==null)
        	return false;
        if(p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right))
        	return true;
        else
        	return false;
        
    }