library

This documentation is automatically generated by online-judge-tools/verification-helper

View the Project on GitHub maspypy/library

:heavy_check_mark: graph/ds/incremental_centroid.hpp

Depends on

Verified with

Code

#include "graph/ds/tree_abelgroup.hpp"
#include "ds/fastset.hpp"

// 木は固定。頂点重みを +1 できる。
// cent: 重心
// max_subtree
template <typename TREE>
struct Incremental_Centroid {
  TREE& tree;
  int N;
  int cent;
  pair<int, int> max_subtree; // (adj, size)
  int wt_sm;
  Tree_AbelGroup<TREE, Monoid_Add<int>, 0, 0, 1> TA;
  FastSet ss;

  Incremental_Centroid(TREE& tree)
      : tree(tree),
        N(tree.N),
        cent(0),
        max_subtree(0, 0),
        wt_sm(0),
        TA(tree),
        ss(N) {}

  int get_subtree_wt(int v) {
    assert(v != cent);
    // cent から見て v 方向
    if (tree.in_subtree(v, cent)) {
      return TA.prod_subtree(tree.jump(cent, v, 1));
    }
    return wt_sm - TA.prod_subtree(cent);
  }

  int move_to(int v) {
    // 圧縮木上で cent から v に進む
    if (tree.in_subtree(v, cent)) {
      // v 方向にある重みの lca
      int a = tree.jump(cent, v, 1);
      int L = tree.LID[a], R = tree.RID[a];
      L = ss.next(L), R = ss.prev(R - 1);
      int x = tree.V[L], y = tree.V[R];
      return tree.lca(x, y);
    }
    int L = tree.LID[cent], R = tree.RID[cent];
    int x = v;
    vc<int> I;
    I.eb(ss.next(0));
    if (1 < L) I.eb(ss.prev(L - 1));
    if (R < N - 1) I.eb(ss.next(R));
    I.eb(ss.prev(N - 1));
    for (auto&& idx: I) {
      if (idx == -1 || idx == N) continue;
      if (L <= idx && idx < R) continue;
      int y = tree.V[idx];
      x = tree.lca_root(x, y, cent);
    }
    return x;
  }

  void add(int v) {
    ss.insert(tree.LID[v]), TA.add(v, 1), wt_sm++;
    if (v == cent) return;
    int wt = get_subtree_wt(v);
    if (max_subtree.se < wt) max_subtree = {tree.jump(cent, v, 1), wt};
    if (2 * wt <= wt_sm) return;
    int k = wt;
    assert(wt_sm == 2 * k - 1);
    int to = move_to(v);
    max_subtree = {tree.jump(to, cent, 1), k - 1};
    cent = to;
  }
};
#line 2 "alg/monoid/add.hpp"

template <typename X>
struct Monoid_Add {
  using value_type = X;
  static constexpr X op(const X &x, const X &y) noexcept { return x + y; }
  static constexpr X inverse(const X &x) noexcept { return -x; }
  static constexpr X power(const X &x, ll n) noexcept { return X(n) * x; }
  static constexpr X unit() { return X(0); }
  static constexpr bool commute = true;
};
#line 3 "ds/fenwicktree/fenwicktree.hpp"

template <typename Monoid>
struct FenwickTree {
  using G = Monoid;
  using E = typename G::value_type;
  int n;
  vector<E> dat;
  E total;

  FenwickTree() {}
  FenwickTree(int n) { build(n); }
  template <typename F>
  FenwickTree(int n, F f) {
    build(n, f);
  }
  FenwickTree(const vc<E>& v) { build(v); }

  void build(int m) {
    n = m;
    dat.assign(m, G::unit());
    total = G::unit();
  }
  void build(const vc<E>& v) {
    build(len(v), [&](int i) -> E { return v[i]; });
  }
  template <typename F>
  void build(int m, F f) {
    n = m;
    dat.clear();
    dat.reserve(n);
    total = G::unit();
    FOR(i, n) { dat.eb(f(i)); }
    for (int i = 1; i <= n; ++i) {
      int j = i + (i & -i);
      if (j <= n) dat[j - 1] = G::op(dat[i - 1], dat[j - 1]);
    }
    total = prefix_sum(m);
  }

  E prod_all() { return total; }
  E sum_all() { return total; }
  E sum(int k) { return prefix_sum(k); }
  E prod(int k) { return prefix_prod(k); }
  E prefix_sum(int k) { return prefix_prod(k); }
  E prefix_prod(int k) {
    chmin(k, n);
    E ret = G::unit();
    for (; k > 0; k -= k & -k) ret = G::op(ret, dat[k - 1]);
    return ret;
  }
  E sum(int L, int R) { return prod(L, R); }
  E prod(int L, int R) {
    chmax(L, 0), chmin(R, n);
    if (L == 0) return prefix_prod(R);
    assert(0 <= L && L <= R && R <= n);
    E pos = G::unit(), neg = G::unit();
    while (L < R) { pos = G::op(pos, dat[R - 1]), R -= R & -R; }
    while (R < L) { neg = G::op(neg, dat[L - 1]), L -= L & -L; }
    return G::op(pos, G::inverse(neg));
  }

  void add(int k, E x) { multiply(k, x); }
  void multiply(int k, E x) {
    static_assert(G::commute);
    total = G::op(total, x);
    for (++k; k <= n; k += k & -k) dat[k - 1] = G::op(dat[k - 1], x);
  }

  template <class F>
  int max_right(const F check) {
    assert(check(G::unit()));
    int i = 0;
    E s = G::unit();
    int k = 1;
    while (2 * k <= n) k *= 2;
    while (k) {
      if (i + k - 1 < len(dat)) {
        E t = G::op(s, dat[i + k - 1]);
        if (check(t)) { i += k, s = t; }
      }
      k >>= 1;
    }
    return i;
  }

  // check(i, x)
  template <class F>
  int max_right_with_index(const F check) {
    assert(check(0, G::unit()));
    int i = 0;
    E s = G::unit();
    int k = 1;
    while (2 * k <= n) k *= 2;
    while (k) {
      if (i + k - 1 < len(dat)) {
        E t = G::op(s, dat[i + k - 1]);
        if (check(i + k, t)) { i += k, s = t; }
      }
      k >>= 1;
    }
    return i;
  }

  int kth(E k) {
    return max_right([&k](E x) -> bool { return x <= k; });
  }
};
#line 2 "graph/tree.hpp"

#line 2 "graph/base.hpp"

template <typename T>
struct Edge {
  int frm, to;
  T cost;
  int id;
};

template <typename T = int, bool directed = false>
struct Graph {
  static constexpr bool is_directed = directed;
  int N, M;
  using cost_type = T;
  using edge_type = Edge<T>;
  vector<edge_type> edges;
  vector<int> indptr;
  vector<edge_type> csr_edges;
  vc<int> vc_deg, vc_indeg, vc_outdeg;
  bool prepared;

  class OutgoingEdges {
  public:
    OutgoingEdges(const Graph* G, int l, int r) : G(G), l(l), r(r) {}

    const edge_type* begin() const {
      if (l == r) { return 0; }
      return &G->csr_edges[l];
    }

    const edge_type* end() const {
      if (l == r) { return 0; }
      return &G->csr_edges[r];
    }

  private:
    const Graph* G;
    int l, r;
  };

  bool is_prepared() { return prepared; }

  Graph() : N(0), M(0), prepared(0) {}
  Graph(int N) : N(N), M(0), prepared(0) {}

  void build(int n) {
    N = n, M = 0;
    prepared = 0;
    edges.clear();
    indptr.clear();
    csr_edges.clear();
    vc_deg.clear();
    vc_indeg.clear();
    vc_outdeg.clear();
  }

  void add(int frm, int to, T cost = 1, int i = -1) {
    assert(!prepared);
    assert(0 <= frm && 0 <= to && to < N);
    if (i == -1) i = M;
    auto e = edge_type({frm, to, cost, i});
    edges.eb(e);
    ++M;
  }

#ifdef FASTIO
  // wt, off
  void read_tree(bool wt = false, int off = 1) { read_graph(N - 1, wt, off); }

  void read_graph(int M, bool wt = false, int off = 1) {
    for (int m = 0; m < M; ++m) {
      INT(a, b);
      a -= off, b -= off;
      if (!wt) {
        add(a, b);
      } else {
        T c;
        read(c);
        add(a, b, c);
      }
    }
    build();
  }
#endif

  void build() {
    assert(!prepared);
    prepared = true;
    indptr.assign(N + 1, 0);
    for (auto&& e: edges) {
      indptr[e.frm + 1]++;
      if (!directed) indptr[e.to + 1]++;
    }
    for (int v = 0; v < N; ++v) { indptr[v + 1] += indptr[v]; }
    auto counter = indptr;
    csr_edges.resize(indptr.back() + 1);
    for (auto&& e: edges) {
      csr_edges[counter[e.frm]++] = e;
      if (!directed)
        csr_edges[counter[e.to]++] = edge_type({e.to, e.frm, e.cost, e.id});
    }
  }

  OutgoingEdges operator[](int v) const {
    assert(prepared);
    return {this, indptr[v], indptr[v + 1]};
  }

  vc<int> deg_array() {
    if (vc_deg.empty()) calc_deg();
    return vc_deg;
  }

  pair<vc<int>, vc<int>> deg_array_inout() {
    if (vc_indeg.empty()) calc_deg_inout();
    return {vc_indeg, vc_outdeg};
  }

  int deg(int v) {
    if (vc_deg.empty()) calc_deg();
    return vc_deg[v];
  }

  int in_deg(int v) {
    if (vc_indeg.empty()) calc_deg_inout();
    return vc_indeg[v];
  }

  int out_deg(int v) {
    if (vc_outdeg.empty()) calc_deg_inout();
    return vc_outdeg[v];
  }

#ifdef FASTIO
  void debug() {
    print("Graph");
    if (!prepared) {
      print("frm to cost id");
      for (auto&& e: edges) print(e.frm, e.to, e.cost, e.id);
    } else {
      print("indptr", indptr);
      print("frm to cost id");
      FOR(v, N) for (auto&& e: (*this)[v]) print(e.frm, e.to, e.cost, e.id);
    }
  }
#endif

  vc<int> new_idx;
  vc<bool> used_e;

  // G における頂点 V[i] が、新しいグラフで i になるようにする
  // {G, es}
  Graph<T, directed> rearrange(vc<int> V, bool keep_eid = 0) {
    if (len(new_idx) != N) new_idx.assign(N, -1);
    if (len(used_e) != M) used_e.assign(M, 0);
    int n = len(V);
    FOR(i, n) new_idx[V[i]] = i;
    Graph<T, directed> G(n);
    vc<int> history;
    FOR(i, n) {
      for (auto&& e: (*this)[V[i]]) {
        if (used_e[e.id]) continue;
        int a = e.frm, b = e.to;
        if (new_idx[a] != -1 && new_idx[b] != -1) {
          history.eb(e.id);
          used_e[e.id] = 1;
          int eid = (keep_eid ? e.id : -1);
          G.add(new_idx[a], new_idx[b], e.cost, eid);
        }
      }
    }
    FOR(i, n) new_idx[V[i]] = -1;
    for (auto&& eid: history) used_e[eid] = 0;
    G.build();
    return G;
  }

private:
  void calc_deg() {
    assert(vc_deg.empty());
    vc_deg.resize(N);
    for (auto&& e: edges) vc_deg[e.frm]++, vc_deg[e.to]++;
  }

  void calc_deg_inout() {
    assert(vc_indeg.empty());
    vc_indeg.resize(N);
    vc_outdeg.resize(N);
    for (auto&& e: edges) { vc_indeg[e.to]++, vc_outdeg[e.frm]++; }
  }
};
#line 4 "graph/tree.hpp"

// HLD euler tour をとっていろいろ。

template <typename GT>
struct Tree {
  using Graph_type = GT;
  GT &G;
  using WT = typename GT::cost_type;
  int N;
  vector<int> LID, RID, head, V, parent, VtoE;
  vc<int> depth;
  vc<WT> depth_weighted;

  Tree(GT &G, int r = 0, bool hld = 1) : G(G) { build(r, hld); }

  void build(int r = 0, bool hld = 1) {
    if (r == -1) return; // build を遅延したいとき

    N = G.N;
    LID.assign(N, -1), RID.assign(N, -1), head.assign(N, r);
    V.assign(N, -1), parent.assign(N, -1), VtoE.assign(N, -1);
    depth.assign(N, -1), depth_weighted.assign(N, 0);
    assert(G.is_prepared());
    int t1 = 0;
    dfs_sz(r, -1, hld);
    dfs_hld(r, t1);
  }

  void dfs_sz(int v, int p, bool hld) {
    auto &sz = RID;
    parent[v] = p;
    depth[v] = (p == -1 ? 0 : depth[p] + 1);
    sz[v] = 1;
    int l = G.indptr[v], r = G.indptr[v + 1];
    auto &csr = G.csr_edges;
    // 使う辺があれば先頭にする

    for (int i = r - 2; i >= l; --i) {
      if (hld && depth[csr[i + 1].to] == -1) swap(csr[i], csr[i + 1]);
    }
    int hld_sz = 0;
    for (int i = l; i < r; ++i) {
      auto e = csr[i];
      if (depth[e.to] != -1) continue;
      depth_weighted[e.to] = depth_weighted[v] + e.cost;
      VtoE[e.to] = e.id;
      dfs_sz(e.to, v, hld);
      sz[v] += sz[e.to];
      if (hld && chmax(hld_sz, sz[e.to]) && l < i) { swap(csr[l], csr[i]); }
    }
  }

  void dfs_hld(int v, int &times) {
    LID[v] = times++;
    RID[v] += LID[v];
    V[LID[v]] = v;
    bool heavy = true;
    for (auto &&e: G[v]) {
      if (depth[e.to] <= depth[v]) continue;
      head[e.to] = (heavy ? head[v] : e.to);
      heavy = false;
      dfs_hld(e.to, times);
    }
  }

  vc<int> heavy_path_at(int v) {
    vc<int> P = {v};
    while (1) {
      int a = P.back();
      for (auto &&e: G[a]) {
        if (e.to != parent[a] && head[e.to] == v) {
          P.eb(e.to);
          break;
        }
      }
      if (P.back() == a) break;
    }
    return P;
  }

  int heavy_child(int v) {
    int k = LID[v] + 1;
    if (k == N) return -1;
    int w = V[k];
    return (parent[w] == v ? w : -1);
  }

  int e_to_v(int eid) {
    auto e = G.edges[eid];
    return (parent[e.frm] == e.to ? e.frm : e.to);
  }
  int v_to_e(int v) { return VtoE[v]; }

  int ELID(int v) { return 2 * LID[v] - depth[v]; }
  int ERID(int v) { return 2 * RID[v] - depth[v] - 1; }

  // 目標地点へ進む個数が k

  int LA(int v, int k) {
    assert(k <= depth[v]);
    while (1) {
      int u = head[v];
      if (LID[v] - k >= LID[u]) return V[LID[v] - k];
      k -= LID[v] - LID[u] + 1;
      v = parent[u];
    }
  }
  int la(int u, int v) { return LA(u, v); }

  int LCA(int u, int v) {
    for (;; v = parent[head[v]]) {
      if (LID[u] > LID[v]) swap(u, v);
      if (head[u] == head[v]) return u;
    }
  }
  // root を根とした場合の lca

  int LCA_root(int u, int v, int root) {
    return LCA(u, v) ^ LCA(u, root) ^ LCA(v, root);
  }
  int lca(int u, int v) { return LCA(u, v); }
  int lca_root(int u, int v, int root) { return LCA_root(u, v, root); }

  int subtree_size(int v, int root = -1) {
    if (root == -1) return RID[v] - LID[v];
    if (v == root) return N;
    int x = jump(v, root, 1);
    if (in_subtree(v, x)) return RID[v] - LID[v];
    return N - RID[x] + LID[x];
  }

  int dist(int a, int b) {
    int c = LCA(a, b);
    return depth[a] + depth[b] - 2 * depth[c];
  }

  WT dist_weighted(int a, int b) {
    int c = LCA(a, b);
    return depth_weighted[a] + depth_weighted[b] - WT(2) * depth_weighted[c];
  }

  // a is in b

  bool in_subtree(int a, int b) { return LID[b] <= LID[a] && LID[a] < RID[b]; }

  int jump(int a, int b, ll k) {
    if (k == 1) {
      if (a == b) return -1;
      return (in_subtree(b, a) ? LA(b, depth[b] - depth[a] - 1) : parent[a]);
    }
    int c = LCA(a, b);
    int d_ac = depth[a] - depth[c];
    int d_bc = depth[b] - depth[c];
    if (k > d_ac + d_bc) return -1;
    if (k <= d_ac) return LA(a, k);
    return LA(b, d_ac + d_bc - k);
  }

  vc<int> collect_child(int v) {
    vc<int> res;
    for (auto &&e: G[v])
      if (e.to != parent[v]) res.eb(e.to);
    return res;
  }

  vc<int> collect_light(int v) {
    vc<int> res;
    bool skip = true;
    for (auto &&e: G[v])
      if (e.to != parent[v]) {
        if (!skip) res.eb(e.to);
        skip = false;
      }
    return res;
  }

  vc<pair<int, int>> get_path_decomposition(int u, int v, bool edge) {
    // [始点, 終点] の"閉"区間列。

    vc<pair<int, int>> up, down;
    while (1) {
      if (head[u] == head[v]) break;
      if (LID[u] < LID[v]) {
        down.eb(LID[head[v]], LID[v]);
        v = parent[head[v]];
      } else {
        up.eb(LID[u], LID[head[u]]);
        u = parent[head[u]];
      }
    }
    if (LID[u] < LID[v]) down.eb(LID[u] + edge, LID[v]);
    elif (LID[v] + edge <= LID[u]) up.eb(LID[u], LID[v] + edge);
    reverse(all(down));
    up.insert(up.end(), all(down));
    return up;
  }

  vc<int> restore_path(int u, int v) {
    vc<int> P;
    for (auto &&[a, b]: get_path_decomposition(u, v, 0)) {
      if (a <= b) {
        FOR(i, a, b + 1) P.eb(V[i]);
      } else {
        FOR_R(i, b, a + 1) P.eb(V[i]);
      }
    }
    return P;
  }
};
#line 3 "graph/ds/tree_abelgroup.hpp"

template <typename TREE, typename AbelGroup, bool edge, bool path_query,
          bool subtree_query>
struct Tree_AbelGroup {
  using MX = AbelGroup;
  using X = typename MX::value_type;
  TREE &tree;
  int N;
  FenwickTree<MX> bit, bit_subtree;

  Tree_AbelGroup(TREE &tree) : tree(tree), N(tree.N) {
    build([](int i) -> X { return MX::unit(); });
  }

  Tree_AbelGroup(TREE &tree, vc<X> &dat) : tree(tree), N(tree.N) {
    build([&](int i) -> X { return dat[i]; });
  }

  template <typename F>
  Tree_AbelGroup(TREE &tree, F f) : tree(tree), N(tree.N) {
    build(f);
  }

  template <typename F>
  void build(F f) {
    vc<X> bit_raw_1(2 * N);
    vc<X> bit_raw_2(N);
    FOR(v, N) {
      X x = MX::unit();
      if (!edge) x = f(v);
      if (edge) x = (v == 0 ? MX::unit() : f(tree.v_to_e(v)));
      bit_raw_1[tree.ELID(v)] = x;
      bit_raw_1[tree.ERID(v)] = MX::inverse(x);
      bit_raw_2[tree.LID[v]] = x;
    }
    if constexpr (path_query) bit.build(bit_raw_1);
    if constexpr (subtree_query) bit_subtree.build(bit_raw_2);
  }

  void add(int i, X x) {
    int v = (edge ? tree.e_to_v(i) : i);
    if constexpr (path_query) {
      bit.add(tree.ELID(v), x);
      bit.add(tree.ERID(v), MX::inverse(x));
    }
    if constexpr (subtree_query) bit_subtree.add(tree.LID[v], x);
  }

  X prod_path(int frm, int to) {
    static_assert(path_query);
    int lca = tree.LCA(frm, to);
    // [frm, lca)

    X x1 = bit.prod(tree.ELID(lca) + 1, tree.ELID(frm) + 1);
    // edge なら (lca, to]、vertex なら [lca, to]

    X x2 = bit.prod(tree.ELID(lca) + edge, tree.ELID(to) + 1);
    return MX::op(x1, x2);
  }

  X prod_subtree(int u) {
    static_assert(subtree_query);
    int l = tree.LID[u], r = tree.RID[u];
    return bit_subtree.prod(l + edge, r);
  }
};
#line 1 "ds/fastset.hpp"
// 64-ary tree

// space: (N/63) * u64

struct FastSet {
  static constexpr u32 B = 64;
  int n, log;
  vvc<u64> seg;

  FastSet() {}
  FastSet(int n) { build(n); }

  template <typename F>
  FastSet(int n, F f) {
    build(n, f);
  }

  void build(int m) {
    seg.clear();
    n = m;
    do {
      seg.push_back(vc<u64>((m + B - 1) / B));
      m = (m + B - 1) / B;
    } while (m > 1);
    log = len(seg);
  }
  template <typename F>
  void build(int n, F f) {
    build(n);
    FOR(i, n) { seg[0][i / B] |= u64(f(i)) << (i % B); }
    FOR(h, log - 1) {
      FOR(i, len(seg[h])) {
        seg[h + 1][i / B] |= u64(bool(seg[h][i])) << (i % B);
      }
    }
  }

  bool operator[](int i) const { return seg[0][i / B] >> (i % B) & 1; }
  void insert(int i) {
    for (int h = 0; h < log; h++) {
      seg[h][i / B] |= u64(1) << (i % B), i /= B;
    }
  }
  void add(int i) { insert(i); }
  void erase(int i) {
    u64 x = 0;
    for (int h = 0; h < log; h++) {
      seg[h][i / B] &= ~(u64(1) << (i % B));
      seg[h][i / B] |= x << (i % B);
      x = bool(seg[h][i / B]);
      i /= B;
    }
  }
  void remove(int i) { erase(i); }

  // min[x,n) or n

  int next(int i) {
    assert(i <= n);
    chmax(i, 0);
    for (int h = 0; h < log; h++) {
      if (i / B == seg[h].size()) break;
      u64 d = seg[h][i / B] >> (i % B);
      if (!d) {
        i = i / B + 1;
        continue;
      }
      i += lowbit(d);
      for (int g = h - 1; g >= 0; g--) {
        i *= B;
        i += lowbit(seg[g][i / B]);
      }
      return i;
    }
    return n;
  }

  // max [0,x], or -1

  int prev(int i) {
    assert(i >= -1);
    if (i >= n) i = n - 1;
    for (int h = 0; h < log; h++) {
      if (i == -1) break;
      u64 d = seg[h][i / B] << (63 - i % B);
      if (!d) {
        i = i / B - 1;
        continue;
      }
      i -= __builtin_clzll(d);
      for (int g = h - 1; g >= 0; g--) {
        i *= B;
        i += topbit(seg[g][i / B]);
      }
      return i;
    }
    return -1;
  }

  // [l, r)

  template <typename F>
  void enumerate(int l, int r, F f) {
    for (int x = next(l); x < r; x = next(x + 1)) f(x);
  }

  string to_string() {
    string s(n, '?');
    for (int i = 0; i < n; ++i) s[i] = ((*this)[i] ? '1' : '0');
    return s;
  }
};
#line 3 "graph/ds/incremental_centroid.hpp"

// 木は固定。頂点重みを +1 できる。
// cent: 重心
// max_subtree
template <typename TREE>
struct Incremental_Centroid {
  TREE& tree;
  int N;
  int cent;
  pair<int, int> max_subtree; // (adj, size)
  int wt_sm;
  Tree_AbelGroup<TREE, Monoid_Add<int>, 0, 0, 1> TA;
  FastSet ss;

  Incremental_Centroid(TREE& tree)
      : tree(tree),
        N(tree.N),
        cent(0),
        max_subtree(0, 0),
        wt_sm(0),
        TA(tree),
        ss(N) {}

  int get_subtree_wt(int v) {
    assert(v != cent);
    // cent から見て v 方向
    if (tree.in_subtree(v, cent)) {
      return TA.prod_subtree(tree.jump(cent, v, 1));
    }
    return wt_sm - TA.prod_subtree(cent);
  }

  int move_to(int v) {
    // 圧縮木上で cent から v に進む
    if (tree.in_subtree(v, cent)) {
      // v 方向にある重みの lca
      int a = tree.jump(cent, v, 1);
      int L = tree.LID[a], R = tree.RID[a];
      L = ss.next(L), R = ss.prev(R - 1);
      int x = tree.V[L], y = tree.V[R];
      return tree.lca(x, y);
    }
    int L = tree.LID[cent], R = tree.RID[cent];
    int x = v;
    vc<int> I;
    I.eb(ss.next(0));
    if (1 < L) I.eb(ss.prev(L - 1));
    if (R < N - 1) I.eb(ss.next(R));
    I.eb(ss.prev(N - 1));
    for (auto&& idx: I) {
      if (idx == -1 || idx == N) continue;
      if (L <= idx && idx < R) continue;
      int y = tree.V[idx];
      x = tree.lca_root(x, y, cent);
    }
    return x;
  }

  void add(int v) {
    ss.insert(tree.LID[v]), TA.add(v, 1), wt_sm++;
    if (v == cent) return;
    int wt = get_subtree_wt(v);
    if (max_subtree.se < wt) max_subtree = {tree.jump(cent, v, 1), wt};
    if (2 * wt <= wt_sm) return;
    int k = wt;
    assert(wt_sm == 2 * k - 1);
    int to = move_to(v);
    max_subtree = {tree.jump(to, cent, 1), k - 1};
    cent = to;
  }
};
Back to top page