// diff for vectors, will return the indeces of the values that are not contained in the other vec.
template < class t >
pair< vector<int>,vector<int> > comp_vectors(vector<t> &vec1, vector<t> &vec2) {
    pair<vector<int>, vector<int> > ret;
    for (int i = 0; i < (signed) vec1.size(); i++) {
        if ( find(vec2.begin(), vec2.end(), vec1[i]) == vec2.end()) {
            ret.first.push_back(i);
        }
            
    }
    for (int i = 0; i < (signed) vec2.size(); i++) {
        if ( find(vec1.begin(), vec1.end(), vec2[i]) == vec1.end()) {
            ret.second.push_back(i);
        }
    }
    return ret;
}