An efficient data structure to hold structure variable with sorting capability

Question

I have a structure

struct dbdetails
{
    int id;
    string val;
};

I need a data structure in C++ that can hold structure variable with a sort capability. Is it possible? I was looking at vector, which can hold structure variable, but I will not be able to sort it based on id, because it is a structure member. Any suggestions?

Answer 1

You need a custom functor for comparing your tries. This should do the trick:

#include <algorithm>
#include <vector>
// try is a keyword. renamed
struct sorthelper : public std::binary_function<try_, try_, bool>
{
    inline bool operator()(const try_& left, const try_& right)
    {   return left.id < right.id;  }
};

...
std::vector<try_> v;
// fill vector 
std::sort(v.begin(), v.end(), sorthelper());
...

Please feel free to ask if you have any follow-up questions. Do you possess the Stroustrup book?

Edit: Suggestion of Matteo:

struct try_
{
    int id;
    string val;
    bool operator<(const try_& other) const
        {return id < other.id;}

}; // no s here plz.

...
std::vector<try_> v;
// fill vector 
std::sort(v.begin(), v.end());
...

Answer 2

You could use a std::map. They are sorted by key, so you could do:

std::map<int, std::string> myStuff;

This is a map with an int as key and std::string as value. When you iterate over the map, you’ll find that it’s automatically sorted by the key.

Note you would no longer need your struct with this solution. If you absolutely need the data in a struct (perhaps to interface with some external library) you could always copy data from the map into a struct as needed.