> For the complete documentation index, see [llms.txt](https://mr-poston-1.gitbook.io/c++/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mr-poston-1.gitbook.io/c++/5.-sets-and-maps/5.3-sets/5.3.1-sets.md).

# 5.3.1 Sets

Sets are a very efficient data structure to store a common group of values like a vector may, but one of the key differences is that a set doesn’t contain duplicates.

Sets are an associative data structure, which means in part that the elements are not stored sequentially and therefore there is no index to look up a value in a set. Instead, sets are stored in a way that makes searching for elements very quick and efficient.