Introduction - If you have any usage issues, please Google them yourself
Set operations: intersection, union and complement (degree of difficulty: 1.1) Collection: uppercase letters ' A' ~ ' Z' requirements to achieve the following functions: 1, a collection of input: Auto remove duplication and illegal character 2, the display of the collection : output all the elements of a collection of 3, the output of a given collection of 4 complement, the output of two given sets and set intersection and