Shared code

#include <bits/stdc++.h>

using namespace std;
using vi = vector<int>;

struct SegmentTree {
    int n;
    vi t;
    SegmentTree(int x) {
        n = x, t.resize(4*n + 1, 0);
        for(int i = 0;i<n;++i) {
            update(1, 0, n - 1, i);
        }
        return;
    }
    void update(int v, int tl, int tr, int p) {
        if (tl == tr) {
            t.at(v) = 1 - t.at(v);
        }
        else {
            int tm = (tl + tr)/2;
            (p <= tm ? update(v*2, tl, tm, p):update(v*2 + 1, tm + 1, tr, p));
            t.at(v) = t.at(v*2) + t.at(v*2 + 1);
        }
        return;
    }
    int query(int v, int tl, int tr, int k) {
        if (tl == tr) {
            return tl;
        }
        int tm = (tl + tr)/2;
        return (k <= t.at(v*2) ? query(v*2, tl, tm, k):query(v*2 + 1, tm + 1, tr, k - t.at(v*2)));
    }
};

int main() {
    int n;
    cin >> n;
    int a[n];
    for(int& v:a) {
        cin >> v;
    }
    SegmentTree T(n);
    for(int i = 0, x;i<n;++i) {
        cin >> x;
        int p = T.query(1, 0, n - 1, x);
        cout << a[p] << ' ';
        T.update(1, 0, n - 1, p);
    }
    cout << endl;
    return 0;
}