C++11 : Compute a rank with a map.

rank_by_field.cpp

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <utility>

struct guy
{
    std::string name_;
    float mark_;
    unsigned int rank_ = 0;
    
    guy(std::string const & name, float mark) : name_(name), mark_(mark)
    {}
};

int main()
{
    // Vector construction
    std::vector<guy> guys;
    guys.push_back(guy("Roger",16.0f));
    guys.push_back(guy("Marcel",10.0f));
    guys.push_back(guy("Robert",12.0f));
    
    // Rank computing
    {
        std::map<float, guy*> sorter;
        for(guy & current_guy : guys) {
            sorter.insert(std::make_pair(current_guy.mark_,&current_guy));
        }
        unsigned int rank = guys.size();
        for(std::pair<float,guy*> const & elem : sorter) {
            elem.second->rank_ = rank;
            --rank;
        }
    }
    
    // Displays the result 
    for(guy const & current_guy : guys) {
        std::cout << current_guy.name_ << " is ranked " << current_guy.rank_ << std::endl;
    }
    
  return 0;
}