树的子结构

	public boolean isSubStructure(TreeNode A, TreeNode B) {
        if (A == null || B == null) return false;
        if (isEqual(A, B)) {
            return true;
        }
        else {
            return isSubStructure(A.left, B) || isSubStructure(A.right, B);
        }
    }
    public boolean isEqual(TreeNode a, TreeNode b) {
        if (b == null) return true;
        if (a == null || a.val != b.val) {
            return false;
        }
        else {
            return isEqual(a.left, b.left) && isEqual(a.right, b.right);
        }
    }