tuple<int, int, int> insert(int data, int pos) {
r.insert(pos, data);
auto it = r.begin() + pos;
int p = prev(it);
int q = next(it);
return make_tuple(p, data, q);
}
tuple<int, int, int> remove(int pos) {
auto it = r.begin() + pos;
int del = *it;
int p = prev(it);
int q = next(it);
r.erase(pos, 1);
return make_tuple(p, del, q);
}
int prev(rope<int>::const_iterator it) {
if (it == r.begin())
return *r.rbegin();
it--;
return *it;
}
int next(rope<int>::const_iterator it) {
it++;
if (it == r.end())
return *r.begin();
return *it;
}
