求转化以下XML文件的样式表写法

Question

原XML文件
<?xml version="1.0" encoding="GB2312"?>
<catalog>
    <cd>
        <title>Empire Burlesque</title>
        <typeid>001</typeid>
        <year>1985</year>
    </cd>
    <cd>
        <title>Hide your heart</title>
        <typeid>002</typeid>
        <year>1985</year>
    </cd>
    <cd>
        <title>Still got the blues</title>
        <typeid>001</typeid>
        <year>1986</year>
    </cd>
</catalog>
要求转成如下格式：
<?xml version="1.0" encoding="GB2312"?>
<Result>
    <Year id = "1985">
        <Typeid num = "001">
<title>Empire Burlesque</title>
        </Typeid>
        <Typeid num = "002">
<title>Hide your heart</title>
        </Typeid>
    </Year>
    <Year id = "1986">
        <Typeid num = "001">
<title>Still got the blues</title>
        </Typeid>
    </Year>
</Result>

Answer 1

我再大体解释下，这意思就是先按year分组，然后再在year中按照typeid分组。求解，感激不尽！