Re: stl map key

From:

Stefan =?UTF-8?B?TsOkd2U=?= <stefan_NOSPAM@NOSPAM_naewe.de>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 11 May 2006 17:42:06 +0200

Message-ID:

<e3vm0a$9er$1@news1.ewetel.de>

andre wrote:

Hi,
anybody can advise how to get a key from the map having value only?
The other way around its easy of course, and map is supposed to be used
like that.
But I need to find a key for a given value.
thanks

This sohould do it:

//--------------------------------------
#include <iostream>
#include <map>
#include <utility>
#include <string>

template<typename T1, typename T2>
struct BySecond
{
    BySecond(const T2& t): t_(t)
        {
        }

    bool operator()(const std::pair<T1, T2>& p) const
    {
         return p.second == t_;
    }
private:

    T2 t_;
};

int main()
{
    std::map<int, std::string> m;

    m[0] = "Null";
    m[1] = "Eins";
    m[2] = "Zwei";

    std::map<int, std::string>::iterator it =
        find_if(m.begin(), m.end(), BySecond<int, std::string>("Zwei"));

    if (it!= m.end())
        std::cout << "Found it: " << it->first << " : " << it->second << std::endl;

    return 0;
}
//--------------------------------------

HTH
  Stefan
--