map iterator

map iterator 是一个pair<key,value>

vector<vector<int>>v;v.push_back({1,4,7});v.push_back({2,5,8});cout<<search(v,5);map<int ,vector<int >>m;m[1].push_back(1);m[1].push_back(2);m[2].push_back(3);m[2].push_back(4);for(auto i=m.begin();i!=m.end();i++){    auto e=i->second;   for(auto ee:e)    cout<<ee;}