nwercstuff.cpp

#include <algorithm>
#include <iostream>
#include <vector>
#include <cmath>
using namespace std;

bool sortfunc(pair<int, int> p1, pair<int, int> p2){
    return pow(p1.first, 2) + pow(p1.second, 2) <
           pow(p2.first, 2) + pow(p2.second, 2);
}

int main(){

    int n; cin >> n;
    vector<pair<int, int>> int_p(n);

    for (auto e : int_p){
        cin >> e.first >> e.second;
    }

    // or use & for basic types.
    int s; cin >> s;
    vector<int> int_vec(s);
    for(auto &e : int_vec){
        cin >> e;
    }

    // also sorting is ez..
    // range is exclusive of end point (i.e. [begin, end) in sort(begin, end) )
    sort(int_vec.begin(), int_vec.end());
    // or
    sort(int_vec.begin(), int_vec.begin() + s);
    
    // sort second half of list based on function (distance).
    sort(int_p.begin()+(n/2), int_p.end(), sortfunc);
}