Two City Scheduling

    static bool cmp (const vector <int> &v1 , const vector <int> &v2)
    {
        return (v1[0] - v1[1] < v2[0] - v2[1]);
    }
    int twoCitySchedCost(vector<vector<int>>& costs) {

        int res = 0;

        sort (costs.begin(), costs.end(), cmp);

        for (int i =  0 ; i < costs.size()/2 ; i++ )
        {
            res += costs[i][0] + (costs[costs.size()/2 + i][1]);
        }
        return res;
    }