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