据说是facebook笔试题，大家看看怎么做

设计一个variant类，这个类有如下特征

variant v = string("jams"); //用string赋值
variant v2 = 18; //用数值型赋值

variant jam["name"] = v; //用variant型赋值
jam["age"] = v2;
jam["sex"] = string("famale");
jam["hobby"] = variant.list_elem(); //“数组”型
variant& hobby = jam["hobby"]; 
hobby[0] = string("basketball");
hobby[1] = string("baseball");
hobby[2] = string("classic music");

const int MAGIC_NUM1 = 0x101010;
const int MAGIC_NUM2 = 0x101011;
hobby[3] = variant(MAGIC_NUM1);  //构造函...
hobby[4] = MAGIC_NUM2;

jam["address"]["state"] = string(""); // "递归"多层
jam["address"]["city"] = string("");

cout << jam["address"]["city"] << ", " << jam["age"] << endl;  //读取