Pre-solución Grafo enorme XOR

#include <bits/stdc++.h>

using namespace std;

struct arista
{
    int desde, hasta, costo;
};

bool operator<(const arista &a, const arista &b)
{
    return a.costo > b.costo;
}

vector <vector <arista> > ady;
vector <int> id;
vector <vector <int> > comp;

bool unionfind(int a, int b)
{
    int idA = id[a];
    int idB = id[b];

    if(idA == idB)
        return false;

    int tA = comp[idA].size();
    int tB = comp[idB].size();

    if(tB > tA)
    {
        swap(a, b);
        swap(idA, idB);
        swap(tA, tB);
    }

    for(int i=0; i<tB; i++)
    {
        comp[idA].push_back(comp[idB][i]);
        id[comp[idB][i]] = idA;
    }

    return true;
}

int main()
{
    int n;
    cin >> n;

    ady.resize(n);
    comp.resize(n);
    id.resize(n);

    for(int i=0; i<n; i++)
    {
        comp[i].push_back(i);
        id[i] = i;
    }

    priority_queue <arista> pq;

    for(int i=0; i<n; i++)
    {
        for(int j=0; j<n; j++)
        {
            if(i != j)
            {
                ady[i].push_back({i, j, i^j});
                pq.push({i, j, i^j});
            }
        }
    }

    vector <arista> MST;

    while(pq.size())
    {
        arista ar = pq.top();
        pq.pop();

        if(unionfind(ar.desde, ar.hasta))
            MST.push_back(ar);
    }

    int sumaTotal = 0;
    map<int, int> mapa;
    for(int i=0; i<MST.size(); i++)
    {
        //cout << MST[i].desde << " a " << MST[i].hasta << " con " << MST[i].costo << endl;
        sumaTotal += MST[i].costo;
        mapa[MST[i].costo]++;
    }

    cout << "Costo total MST: " << sumaTotal << endl;

    for(auto i:mapa)
    {
        cout << i.first << ": " << i.second << endl;
    }

    return 0;
}