这个error是什么意思呀

Question

[Error] no match for 'operator<<' (operand types are 'std::ostream {aka std::basic_ostream<char>}' and 'std::set<int>::iterator {aka std::_Rb_tree_const_iterator<int>}')

Answer 1

运算符不匹配，你<<后面的参数类型不支持