Function insert

code/data-structures/sqrt_decomposition.cpp:29–31

  T[i] = segment(vi(T[i].arr.begin(), T[i].arr.begin() + at));
  return i + 1; }
void insert(int at, int v) {
  vi arr; arr.push_back(v);
  T.insert(T.begin() + split(at), segment(arr)); }
void erase(int at) {
  int i = split(at); split(at + 1);
  T.erase(T.begin() + i); }