Problem p02373 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
using Int = long long;
// BEGIN CUT HERE
struct HLDecomposition {
  int n, pos;
  vector<vector<int>> G;
  vector<int> vid, head, sub, hvy, par, dep, inv, type;

  HLDecomposition() {}
  HLDecomposition(int sz)
      : n(sz), pos(0), G(n), vid(n, -1), head(n), sub(n, 1), hvy(n, -1), par(n),
        dep(n), inv(n), type(n) {}

  void add_edge(int u, int v) {
    G[u].push_back(v);
    G[v].push_back(u);
  }

  void build(vector<int> rs = vector<int>(1, 0)) {
    int c = 0;
    for (int r : rs) {
      dfs(r);
      bfs(r, c++);
    }
  }

  void dfs(int rt) {
    using T = pair<int, int>;
    stack<T> st;
    dep[rt] = 0;
    st.emplace(rt, 0);
    while (!st.empty()) {
      int v = st.top().first;
      int &i = st.top().second;
      if (i < (int)G[v].size()) {
        int u = G[v][i++];
        if (u == par[v])
          continue;
        par[u] = v;
        dep[u] = dep[v] + 1;
        st.emplace(u, 0);
      } else {
        st.pop();
        int res = 0;
        for (int u : G[v]) {
          if (u == par[v])
            continue;
          sub[v] += sub[u];
          if (res < sub[u])
            res = sub[u], hvy[v] = u;
        }
      }
    }
  }

  void bfs(int r, int c) {
    int &k = pos;
    queue<int> q({r});
    while (!q.empty()) {
      int h = q.front();
      q.pop();
      for (int i = h; i != -1; i = hvy[i]) {
        type[i] = c;
        vid[i] = k++;
        inv[vid[i]] = i;
        head[i] = h;
        for (int j : G[i])
          if (j != par[i] && j != hvy[i])
            q.push(j);
      }
    }
  }

  // for_each(vertex)
  // [l,r] <- attention!!
  void for_each(int u, int v, const function<void(int, int)> &f) {
    while (1) {
      if (vid[u] > vid[v])
        swap(u, v);
      f(max(vid[head[v]], vid[u]), vid[v]);
      if (head[u] != head[v])
        v = par[head[v]];
      else
        break;
    }
  }

  // for_each(edge)
  // [l,r] <- attention!!
  void for_each_edge(int u, int v, const function<void(int, int)> &f) {
    while (1) {
      if (vid[u] > vid[v])
        swap(u, v);
      if (head[u] != head[v]) {
        f(vid[head[v]], vid[v]);
        v = par[head[v]];
      } else {
        if (u != v)
          f(vid[u] + 1, vid[v]);
        break;
      }
    }
  }

  int lca(int u, int v) {
    while (1) {
      if (vid[u] > vid[v])
        swap(u, v);
      if (head[u] == head[v])
        return u;
      v = par[head[v]];
    }
  }

  int distance(int u, int v) { return dep[u] + dep[v] - 2 * dep[lca(u, v)]; }
};
// END CUT HERE

signed main() {
  int n;
  cin >> n;
  HLDecomposition lca(n);
  for (int i = 0; i < n; i++) {
    int k;
    cin >> k;
    for (int j = 0; j < k; j++) {
      int c;
      cin >> c;
      lca.add_edge(i, c);
    }
  }
  lca.build();
  int q;
  cin >> q;
  while (q--) {
    int u, v;
    cin >> u >> v;
    cout << lca.lca(u, v) << endl;
  }
  return 0;
}
/*
  verified on 2017/11/07
  http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_5_C&lang=jp
*/

/*

struct BiconectedGraph{
  typedef pair<int,int> P;
  int n;
  vector<vector<int> > G,C,T;
  vector<int> ord,low,belong;
  vector<P> B;
  BiconectedGraph(){}
  BiconectedGraph(int sz):n(sz),G(sz),C(sz),T(sz){}

   void add_edge(int u,int v){
    G[u].push_back(v);
    G[v].push_back(u);
  }

   void input(int m,int offset){
    int a,b;
    for(int i=0;i<m;i++){
      scanf("%d %d",&a,&b);
      add_edge(a+offset,b+offset);
    }
  }

   bool is_bridge(int u,int v){
    if(ord[u]>ord[v]) swap(u,v);
    return ord[u]<low[v];
  }

  void dfs(int u,int p,int &k){
    ord[u]=low[u]=k;
    ++k;
    for(int v:G[u]){
      if(v==p) continue;
      if(ord[v]>=0){
        low[u]=min(low[u],ord[v]);
      }else{
        dfs(v,u,k);
        low[u]=min(low[u],low[v]);
      }
      if(is_bridge(u,v)) B.push_back(P(u,v));
    }
  }

  void fill_component(int c,int u){
    C[c].push_back(u);
    belong[u]=c;
    for(int v:G[u]){
      if(belong[v]>=0||is_bridge(u,v)) continue;
      fill_component(c,v);
    }
  }

  void add_component(int u,int &k){
    if(belong[u]>=0) return;
    fill_component(k++,u);
  }

  int build(){
    int k=0;
    ord.resize(n);
    low.resize(n);
    belong.resize(n);
    fill(ord.begin(),ord.end(),-1);
    fill(belong.begin(),belong.end(),-1);
    for(int u=0;u<n;u++){
      if(ord[u]>=0) continue;
      dfs(u,-1,k);
    }
    k=0;
    for(int i=0;i<(int)B.size();i++){
      add_component(B[i].first,k);
      add_component(B[i].second,k);
    }
    for(int u=0;u<n;u++) add_component(u,k);
    for(int i=0;i<(int)B.size();i++){
      int u=belong[B[i].first],v=belong[B[i].second];
      T[u].push_back(v);
      T[v].push_back(u);
    }
    return k;
  }
};

template <typename T,typename E>
struct SegmentTree{
  typedef function<T(T,T)> F;
  typedef function<T(T,E)> G;
  int n;
  F f;
  G g;
  T d1;
  E d0;
  vector<T> dat;
  SegmentTree(){};
  SegmentTree(int n_,F f,G g,T d1,
              vector<T> v=vector<T>()):
    f(f),g(g),d1(d1){
    init(n_);
    if(n_==(int)v.size()) build(n_,v);
  }
  void init(int n_){
    n=1;
    while(n<n_) n*=2;
    dat.clear();
    dat.resize(2*n-1,d1);
  }
  void build(int n_, vector<T> v){
    for(int i=0;i<n_;i++) dat[i+n-1]=v[i];
    for(int i=n-2;i>=0;i--)
      dat[i]=f(dat[i*2+1],dat[i*2+2]);
  }
  void update(int k,E a){
    k+=n-1;
    dat[k]=g(dat[k],a);
    while(k>0){
      k=(k-1)/2;
      dat[k]=f(dat[k*2+1],dat[k*2+2]);
    }
  }
  inline T query(int a,int b){
    T vl=d1,vr=d1;
    for(int l=a+n,r=b+n;l<r;l>>=1,r>>=1) {
      if(l&1) vl=f(vl,dat[(l++)-1]);
      if(r&1) vr=f(dat[(--r)-1],vr);
    }
    return f(vl,vr);
  }

};

signed main(){
  int n,e,q;
  scanf("%d %d %d",&n,&e,&q);

  BiconectedGraph big(n);
  big.input(e,-1);

  int E=0,V=big.build();
  HLDecomposition hl(V);
  for(int i=0;i<V;i++)
    for(int j:big.T[i])
      if(i<j) hl.add_edge(i,j),E++;

  hl.build();
  SegmentTree<int,int> rmq(V,
                           [](int a,int b){return max(a,b);},
                           [](int a,int b){return b;},
                           -1);
  vector<priority_queue<int> > pq(V);
  map<int,int> m;
  int num=0;
  for(int i=0;i<q;i++){
    int d;
    scanf("%d",&d);
    if(d==1){
      int u,w;
      scanf("%d %d",&u,&w);
      u--;
      u=big.belong[u];
      u=hl.vid[u];
      m[w]=u;
      if(pq[u].empty()||pq[u].top()<w) rmq.update(u,w);
      pq[u].push(w);
      num++;
    }
    if(d==2){
      int s,t;
      scanf("%d %d",&s,&t);
      s--;t--;
      s=big.belong[s];
      t=big.belong[t];
      int ans=-1;
      hl.for_each(s, t, [&](int l, int r) {
          ans = max(ans,rmq.query(l, r + 1));
        });
      printf("%d\\n",ans);
      if(~ans){
        int k=m[ans];
        pq[k].pop();
        rmq.update(k,(!pq[k].empty()?pq[k].top():-1));
        num--;
      }
    }
  }
  return 0;
}

/* verified on 2017/11/07
https://yukicoder.me/problems/no/529
*/

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
using Int = long long;
// BEGIN CUT HERE
struct HLDecomposition {
  int n, pos;
  vector<vector<int>> G;
  vector<int> vid, head, sub, hvy, par, dep, inv, type;

  HLDecomposition() {}
  HLDecomposition(int sz)
      : n(sz), pos(0), G(n), vid(n, -1), head(n), sub(n, -1), hvy(n, -1),
        par(n), dep(n), inv(n), type(n) {}

  void add_edge(int u, int v) {
    G[u].push_back(v);
    G[v].push_back(u);
  }

  void build(vector<int> rs = vector<int>(1, 0)) {
    int c = 0;
    for (int r : rs) {
      dfs(r);
      bfs(r, c++);
    }
  }

  void dfs(int rt) {
    using T = pair<int, int>;
    stack<T> st;
    st.emplace(rt, 0);
    while (!st.empty()) {
      int v = st.top().first;
      int &i = st.top().second;
      if (i < (int)G[v].size()) {
        int u = G[v][i++];
        if (u == par[v])
          continue;
        par[u] = v;
        st.emplace(u, 0);
      } else {
        st.pop();
        int res = 0;
        for (int u : G[v]) {
          if (u == par[v])
            continue;
          sub[v] += sub[u];
          if (res < sub[u])
            res = sub[u], hvy[v] = u;
        }
      }
    }
  }

  void bfs(int r, int c) {
    int &k = pos;
    queue<int> q({r});
    while (!q.empty()) {
      int h = q.front();
      q.pop();
      for (int i = h; i != -1; i = hvy[i]) {
        type[i] = c;
        vid[i] = k++;
        inv[vid[i]] = i;
        head[i] = h;
        for (int j : G[i])
          if (j != par[i] && j != hvy[i])
            q.push(j);
      }
    }
  }

  // for_each(vertex)
  // [l,r] <- attention!!
  void for_each(int u, int v, const function<void(int, int)> &f) {
    while (1) {
      if (vid[u] > vid[v])
        swap(u, v);
      f(max(vid[head[v]], vid[u]), vid[v]);
      if (head[u] != head[v])
        v = par[head[v]];
      else
        break;
    }
  }

  // for_each(edge)
  // [l,r] <- attention!!
  void for_each_edge(int u, int v, const function<void(int, int)> &f) {
    while (1) {
      if (vid[u] > vid[v])
        swap(u, v);
      if (head[u] != head[v]) {
        f(vid[head[v]], vid[v]);
        v = par[head[v]];
      } else {
        if (u != v)
          f(vid[u] + 1, vid[v]);
        break;
      }
    }
  }

  int lca(int u, int v) {
    while (1) {
      if (vid[u] > vid[v])
        swap(u, v);
      if (head[u] == head[v])
        return u;
      v = par[head[v]];
    }
  }

  int distance(int u, int v) { return dep[u] + dep[v] - 2 * dep[lca(u, v)]; }
};
// END CUT HERE

signed main() {
  int n;
  cin >> n;
  HLDecomposition lca(n);
  for (int i = 0; i < n; i++) {
    int k;
    cin >> k;
    for (int j = 0; j < k; j++) {
      int c;
      cin >> c;
      lca.add_edge(i, c);
    }
  }
  lca.build();
  int q;
  cin >> q;
  while (q--) {
    int u, v;
    cin >> u >> v;
    cout << lca.lca(u, v) << endl;
  }
  return 0;
}
/*
  verified on 2017/11/07
  http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_5_C&lang=jp
*/

/*

struct BiconectedGraph{
  typedef pair<int,int> P;
  int n;
  vector<vector<int> > G,C,T;
  vector<int> ord,low,belong;
  vector<P> B;
  BiconectedGraph(){}
  BiconectedGraph(int sz):n(sz),G(sz),C(sz),T(sz){}

   void add_edge(int u,int v){
    G[u].push_back(v);
    G[v].push_back(u);
  }

   void input(int m,int offset){
    int a,b;
    for(int i=0;i<m;i++){
      scanf("%d %d",&a,&b);
      add_edge(a+offset,b+offset);
    }
  }

   bool is_bridge(int u,int v){
    if(ord[u]>ord[v]) swap(u,v);
    return ord[u]<low[v];
  }

  void dfs(int u,int p,int &k){
    ord[u]=low[u]=k;
    ++k;
    for(int v:G[u]){
      if(v==p) continue;
      if(ord[v]>=0){
        low[u]=min(low[u],ord[v]);
      }else{
        dfs(v,u,k);
        low[u]=min(low[u],low[v]);
      }
      if(is_bridge(u,v)) B.push_back(P(u,v));
    }
  }

  void fill_component(int c,int u){
    C[c].push_back(u);
    belong[u]=c;
    for(int v:G[u]){
      if(belong[v]>=0||is_bridge(u,v)) continue;
      fill_component(c,v);
    }
  }

  void add_component(int u,int &k){
    if(belong[u]>=0) return;
    fill_component(k++,u);
  }

  int build(){
    int k=0;
    ord.resize(n);
    low.resize(n);
    belong.resize(n);
    fill(ord.begin(),ord.end(),-1);
    fill(belong.begin(),belong.end(),-1);
    for(int u=0;u<n;u++){
      if(ord[u]>=0) continue;
      dfs(u,-1,k);
    }
    k=0;
    for(int i=0;i<(int)B.size();i++){
      add_component(B[i].first,k);
      add_component(B[i].second,k);
    }
    for(int u=0;u<n;u++) add_component(u,k);
    for(int i=0;i<(int)B.size();i++){
      int u=belong[B[i].first],v=belong[B[i].second];
      T[u].push_back(v);
      T[v].push_back(u);
    }
    return k;
  }
};

template <typename T,typename E>
struct SegmentTree{
  typedef function<T(T,T)> F;
  typedef function<T(T,E)> G;
  int n;
  F f;
  G g;
  T d1;
  E d0;
  vector<T> dat;
  SegmentTree(){};
  SegmentTree(int n_,F f,G g,T d1,
              vector<T> v=vector<T>()):
    f(f),g(g),d1(d1){
    init(n_);
    if(n_==(int)v.size()) build(n_,v);
  }
  void init(int n_){
    n=1;
    while(n<n_) n*=2;
    dat.clear();
    dat.resize(2*n-1,d1);
  }
  void build(int n_, vector<T> v){
    for(int i=0;i<n_;i++) dat[i+n-1]=v[i];
    for(int i=n-2;i>=0;i--)
      dat[i]=f(dat[i*2+1],dat[i*2+2]);
  }
  void update(int k,E a){
    k+=n-1;
    dat[k]=g(dat[k],a);
    while(k>0){
      k=(k-1)/2;
      dat[k]=f(dat[k*2+1],dat[k*2+2]);
    }
  }
  inline T query(int a,int b){
    T vl=d1,vr=d1;
    for(int l=a+n,r=b+n;l<r;l>>=1,r>>=1) {
      if(l&1) vl=f(vl,dat[(l++)-1]);
      if(r&1) vr=f(dat[(--r)-1],vr);
    }
    return f(vl,vr);
  }

};

signed main(){
  int n,e,q;
  scanf("%d %d %d",&n,&e,&q);

  BiconectedGraph big(n);
  big.input(e,-1);

  int E=0,V=big.build();
  HLDecomposition hl(V);
  for(int i=0;i<V;i++)
    for(int j:big.T[i])
      if(i<j) hl.add_edge(i,j),E++;

  hl.build();
  SegmentTree<int,int> rmq(V,
                           [](int a,int b){return max(a,b);},
                           [](int a,int b){return b;},
                           -1);
  vector<priority_queue<int> > pq(V);
  map<int,int> m;
  int num=0;
  for(int i=0;i<q;i++){
    int d;
    scanf("%d",&d);
    if(d==1){
      int u,w;
      scanf("%d %d",&u,&w);
      u--;
      u=big.belong[u];
      u=hl.vid[u];
      m[w]=u;
      if(pq[u].empty()||pq[u].top()<w) rmq.update(u,w);
      pq[u].push(w);
      num++;
    }
    if(d==2){
      int s,t;
      scanf("%d %d",&s,&t);
      s--;t--;
      s=big.belong[s];
      t=big.belong[t];
      int ans=-1;
      hl.for_each(s, t, [&](int l, int r) {
          ans = max(ans,rmq.query(l, r + 1));
        });
      printf("%d\\n",ans);
      if(~ans){
        int k=m[ans];
        pq[k].pop();
        rmq.update(k,(!pq[k].empty()?pq[k].top():-1));
        num--;
      }
    }
  }
  return 0;
}

/* verified on 2017/11/07
https://yukicoder.me/problems/no/529
*/