kruskal algorithm in C++

kruskal.cc

#include <iostream>

template<typename T=int>
class edgeType{
private:
    char from;
    char to;
    T w;
public:
    edgeType(char a, char b, int c):from(a),to(b),w(c) {} 
    T getW() const {return w;}
    T getFrom() const {return from;}
    T getTo() const {return to;}
    bool operator < (const edgeType<T> & right) const {
        return w < right.getW();
    }
};

template<typename T>
void printMST(const std::vector<edgeType<T> > & mst) {
    for(const auto it: mst){
        std::cout<<"("<<it.getFrom()<<","<<it.getTo()<<","<<it.getW()<<") ";
    }
    std::cout<<std::endl;
}
 
int union_find(const int & from, vector<int> & arr){
    if(arr[from] == from){
        return from;
    }
    return union_find(arr[from], arr);
}

void union_set(const int & from, const int & to, vector<int> & arr){    
    arr[union_find(to, arr)] = arr[from];
}

template<typename T>
std::vector<edgeType<T> > kruskal(const std::vector<char> & nodes, std::vector<edgeType<T> > & edges){
    std::vector<edgeType<T> > mst;
    std::vector<int> arr;
    for(const auto & it: nodes){
        arr.push_back(it-'A');
    }
    std::sort(edges.begin(), edges.end());
    for(const auto & it : edges){
        int from = it.getFrom() - 'A';
        int to = it.getTo() - 'A';
        T w = it.getW();
        if( union_find(from, arr) != union_find(to, arr)){
            mst.push_back(edgeType<T>(from, to, w));
            union_set(from, to, arr);
        }
    }
    return mst;
}

int main() {    
    std::vector<char> nodes = {'A','B','C','D','E','F','G'};   
    std::vector< edgeType<int> > edges = { edgeType<int>('A', 'B', 7), edgeType<int>('A', 'D', 5),
      edgeType<int>('B', 'C', 8), edgeType<int>('B', 'D', 9), edgeType<int>('B', 'E', 7),
      edgeType<int>('C', 'E', 5), edgeType<int>('D', 'E', 15), edgeType<int>('D', 'F', 6),
      edgeType<int>('E', 'F', 8), edgeType<int>('E', 'G', 9), edgeType<int>('F', 'G', 11)};
    std::vector<edgeType<int> > mst_k = kruskal(nodes, edges);    
    std::cout<<"kruskal: ";
    printMST(mst_k);
    return 0;
}