超集

superset：超集，扩展集，父集

 Definition:
 A set S1 is a superset of another set S2 if every element in S2 is in S1.
跟子集相应。
S1是S2的超集，则S2是S1的子集。

超集

superset：超集，扩展集，父集

 Definition:
 A set S1 is a superset of another set S2 if every element in S2 is in S1.
跟子集相应。
S1是S2的超集，则S2是S1的子集。