append if not contains.

StrContains => Contains StringSliceEqual => Equal StringSliceMergeSorted => MergeSorted Contains checks if a list contains a string.

对一个字符串数组去重.

Equal compares two string slices for equality.

排除一个项目中符合条件的成员，并返回一个新的slice.

MergeSorted takes two string slices that are assumed to be sorted and does a zipper merge of the two sorted slices, removing any cross-slice duplicates.