gistfile1.cpp

#include <set>
#include <utility>
#include <iostream>
#include <initializer_list>
#include <algorithm>
#include <math.h>

std::set<int> divisors(int n)
{
    std::set<int> divs;
    divs.insert(1);
    for (int i = 2; i < sqrt(n) + 1; ++i)
        if (n % i == 0)
            divs.insert({i, n/i});
    return divs;
}

int sumdiv(int n)
{
    const auto& divs = divisors(n);
    return std::accumulate(divs.begin(), divs.end(), 0);
}

std::pair<int,int> apair(int x)
{
    int b = sumdiv(x);
    return std::make_pair(std::min(x,b), std::max(x,b));
}

bool haspair(int x)
{
    return (sumdiv(x) != x) && (sumdiv(sumdiv(x)) == x);
}

std::set<std::pair<int,int>> amicable_pairs(int count)
{
    int x = 1;
    std::set<std::pair<int,int>> results;
    while(1)
    {
        if (haspair(x))
            results.insert(apair(x));
        if (results.size() >= count)
            break;
        ++x;
    }
    return results;
}

int main()
{
    for (auto x: amicable_pairs(10))
        std::cout << "(" << x.first << ", " << x.second << "), ";
    std::cout << "\n";
}