server-whatever/a.cpp

#include <unordered_map>
#include <iostream>
int main()
{
        std::unordered_map<int, std::string> c = {{1, "one"}, {2, "two"}, {3, "three"},
                                                {4, "four"}, {5, "five"}, {6, "six"}};
            // 从 c 擦除所有奇数
            for(auto it = c.begin(); it != c.end(); )
                      if(it->first % 2 == 1)
                                    it = c.erase(it);
                    else
                                  ++it;
                c.erase(2);
                c.erase(2);
                c.erase(7);
                for(auto& p : c)
                          std::cout << p.second << ' '<<std::endl;
                std::string s="";
                std::cout << std::stoi(s)<<std::endl;
}