[TOC] ## std::set ``` set<string>a; a.insert("a"); a.insert("b"); for (auto item : a) { cout << item << "\n"; } ``` ## std::unordered_set 无序 set ### std::unordered_multiset 允许重复 元素 ``` unordered_multiset<string>a; a.insert("a"); a.insert("a"); for (auto item : a) { cout << item << "\n"; } ```