K-Way Merge using C++11

kwaymerge.cpp

template <typename T>
using minheap = priority_queue<T, vector<T>, greater>;

vector<int> kwaymerge(vector<vector<int>>& vs) {
    int k = vs.size();
    vector<int> readcount(k, 0);
    vector<int> res;
    vector<pair<int, int>> vec;
    for (int i = 0; i < k; i++) {
        if (vs[i].size() > 0){
           vec.push_back(make_pair(vs[i].front(), i));
           readcount[i]++;
        }
    }
    // this way it uses heapify
    minheap q(vec.begin(), vec.end());
    
    while (!q.empty()) {
        int v = q.top().first, i = q.top().second; q.pop();
        res.push_back(v);
        if (readcount[i] < vs[i].size()) {
           vec.push_back(make_pair(vs[i][readcount[i], i));
           readcount[i]++;
        }
    }
}