[ programmation en c++ ]

#include <set>
#include <iostream>

typedef std::pair<unsigned int,unsigned int> point_t;

unsigned int milieu(const std::set<point_t> & points){
    std::set<point_t>::const_iterator
        sit (points.begin()),
        send(points.end());
    for(unsigned int n=0;sit!=send;++sit,++n){
        if(n>=points.size()/2) return sit->first;
    }
    return 0;
}

int main(){
    std::set<point_t> points;
    points.insert(std::make_pair(3,5));
    points.insert(std::make_pair(6,9));
    points.insert(std::make_pair(2,8));
    points.insert(std::make_pair(1,1));
    std::cout << "xmilieu = " << milieu(points) << std::endl;
    return 0;
}