Find pair by key within a vector of pairs

you don’t need use find, please use find_if, this is the link:http://www.cplusplus.com/reference/algorithm/find_if/

auto it = std::find_if( sortList.begin(), sortList.end(),
    [&User](const std::pair<std::string, int>& element){ return element.first == User.name;} );

If you are using C++ standard before C++11, later, you’ll need a function instead of a lambda:

bool isEqual(const std::pair<std::string, int>& element)
{
    return element.first ==  User.name;
}
it = std::find_if( sortList.begin(), sortList.end(), isEqual );