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