第八周作业

public static void main() {
    Node header1, header2;
    Map map = new HashMap();
    int index = 0;
    while (header1 != null) {
        map.put(header1, index++);
      	header1 = header1.next();
    }
    while (header2 != null) {
        if (map.containsKey(header2)) {
            return header2;
        }
      	header2 = header2.next();
    }
    
    return null;
}