Method upd

Data Structures/Persistent UnionFind.cpp:39–42

update the ith value if the rth array by x and return the new root of the array

  }
  // update the ith value if the rth array by x and return the new root of the array
  int upd(int r, int i, T x) {
    root.push_back(upd(root[r], i, x, 0, n - 1));
    return root.size() - 1;
  }
  void set(int r, int i, T x) {
    int k = upd(r, i, x);
    root[r] = root[k];