Question

I was wondering, is there any way to perform random access in multimap’s values.

#include <map>
#include <vector>
#include <string>

int main() {
    std::map<std::string, std::vector<std::string>> m0;

    m0["Food"].push_back("Ice Cream");
    m0["Food"].push_back("Pizza");

    // Random access to Pizza. Nice!
    printf ("2nd Food is %s\n", m0["Food"][1].c_str());

    std::multimap<std::string, std::string> m1;
    m1.insert(std::pair<std::string, std::string>("Food", "Ice Cream"));
    m1.insert(std::pair<std::string, std::string>("Food", "Pizza"));

    // Is there any way to perform random access in multimap?
    std::multimap<std::string, std::string>::const_iterator find = m1.find("Food");

    // Sequential access to Pizza. Bad :(
    // I wish to have something
    // printf ("2nd Food is %s\n", find[1].c_str());
    find++;
    printf ("2nd Food is %s\n", find->second.c_str());

    getchar();
}

Since random access to map’s values is one of the requirement, is it better to use map of vector then?

Answer 1

std::multimap<>‘s iterators are strictly bidirectional (§23.3.2/1), so no, random-access between values with the same key is not possible.