lmori's Library

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:heavy_check_mark: verify/LibraryChecker/tree/LowestCommonAncestor2.test.cpp

Depends on

Code

#include "../../../template/template.hpp"
#define PROBLEM "https://judge.yosupo.jp/problem/lca"
#include "../../../graph/tree/LowestCommonAncestor.hpp"

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int n, q;
  in(n, q);
  TreeQuery t(n);
  rep(i, 1, n) {
    int p;
    in(p);
    t.add_edge(i, p);
  }
  rep(i, q) {
    int u, v;
    in(u, v);
    out(t.lca(u, v));
  }
}
#line 2 "template/template.hpp"
#pragma region Macros
#include <bits/stdc++.h>
#include <tr2/dynamic_bitset>

using namespace std;
using namespace tr2;
using lint = long long;
using ull = unsigned long long;
using ld = long double;
using int128 = __int128_t;
#define all(x) (x).begin(), (x).end()
#define uniqv(v) v.erase(unique(all(v)), v.end())
#define OVERLOAD_REP(_1, _2, _3, name, ...) name
#define REP1(i, n) for (auto i = std::decay_t<decltype(n)>{}; (i) != (n); ++(i))
#define REP2(i, l, r) for (auto i = (l); (i) != (r); ++(i))
#define rep(...) OVERLOAD_REP(__VA_ARGS__, REP2, REP1)(__VA_ARGS__)
#define logfixed(x) cout << fixed << setprecision(10) << x << endl;

ostream &operator<<(ostream &dest, __int128_t value) {
  ostream::sentry s(dest);
  if (s) {
    __uint128_t tmp = value < 0 ? -value : value;
    char buffer[128];
    char *d = end(buffer);
    do {
      --d;
      *d = "0123456789"[tmp % 10];
      tmp /= 10;
    } while (tmp != 0);
    if (value < 0) {
      --d;
      *d = '-';
    }
    int len = end(buffer) - d;
    if (dest.rdbuf()->sputn(d, len) != len) {
      dest.setstate(ios_base::badbit);
    }
  }
  return dest;
}

template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != (int)v.size() ? " " : "");
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, const set<T> &set_var) {
  for (auto itr = set_var.begin(); itr != set_var.end(); itr++) {
    os << *itr;
    ++itr;
    if (itr != set_var.end()) os << " ";
    itr--;
  }
  return os;
}

template <typename T>
ostream &operator<<(ostream &os, const unordered_set<T> &set_var) {
  for (auto itr = set_var.begin(); itr != set_var.end(); itr++) {
    os << *itr;
    ++itr;
    if (itr != set_var.end()) os << " ";
    itr--;
  }
  return os;
}

template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &map_var) {
  for (auto itr = map_var.begin(); itr != map_var.end(); itr++) {
    os << itr->first << " -> " << itr->second << "\n";
  }
  return os;
}

template <typename T, typename U>
ostream &operator<<(ostream &os, const unordered_map<T, U> &map_var) {
  for (auto itr = map_var.begin(); itr != map_var.end(); itr++) {
    os << itr->first << " -> " << itr->second << "\n";
  }
  return os;
}

template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &pair_var) {
  os << pair_var.first << " " << pair_var.second;
  return os;
}

void out() { cout << '\n'; }
template <class T, class... Ts>
void out(const T &a, const Ts &...b) {
  cout << a;
  (cout << ... << (cout << ' ', b));
  cout << '\n';
}

void outf() { cout << '\n'; }
template <class T, class... Ts>
void outf(const T &a, const Ts &...b) {
  cout << fixed << setprecision(14) << a;
  (cout << ... << (cout << ' ', b));
  cout << '\n';
}

template <typename T>
istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v) is >> in;
  return is;
}

inline void in(void) { return; }
template <typename First, typename... Rest>
void in(First &first, Rest &...rest) {
  cin >> first;
  in(rest...);
  return;
}

template <typename T>
bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

vector<lint> dx8 = {1, 1, 0, -1, -1, -1, 0, 1};
vector<lint> dy8 = {0, 1, 1, 1, 0, -1, -1, -1};
vector<lint> dx4 = {1, 0, -1, 0};
vector<lint> dy4 = {0, 1, 0, -1};

#pragma endregion
#line 2 "verify/LibraryChecker/tree/LowestCommonAncestor2.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/lca"
#line 2 "data-structure/segment-tree/SegmentTree.hpp"
template <class S, auto op, auto e>
struct segtree {
 private:
  unsigned int seg_bit_ceil(unsigned int n) {
    unsigned int x = 1;
    while (x < (unsigned int)(n)) x *= 2;
    return x;
  }

 public:
  static_assert(std::is_convertible_v<decltype(op), std::function<S(S, S)>>,
                "op must work as S(S, S)");
  static_assert(std::is_convertible_v<decltype(e), std::function<S()>>,
                "e must work as S()");
  segtree() : segtree(0) {}
  explicit segtree(int n) : segtree(std::vector<S>(n, e())) {}
  explicit segtree(const std::vector<S>& v) : _n(int(v.size())) {
    size = (int)seg_bit_ceil((unsigned int)(_n));
    log = __builtin_ctz((unsigned int)size);
    d = std::vector<S>(2 * size, e());
    for (int i = 0; i < _n; i++) d[size + i] = v[i];
    for (int i = size - 1; i >= 1; i--) {
      update(i);
    }
  }

  void set(int p, S x) {
    assert(0 <= p && p < _n);
    p += size;
    d[p] = x;
    for (int i = 1; i <= log; i++) update(p >> i);
  }

  S get(int p) const {
    assert(0 <= p && p < _n);
    return d[p + size];
  }

  S prod(int l, int r) const {
    assert(0 <= l && l <= r && r <= _n);
    S sml = e(), smr = e();
    l += size;
    r += size;

    while (l < r) {
      if (l & 1) sml = op(sml, d[l++]);
      if (r & 1) smr = op(d[--r], smr);
      l >>= 1;
      r >>= 1;
    }
    return op(sml, smr);
  }

  S all_prod() const { return d[1]; }

  template <bool (*f)(S)>
  int max_right(int l) const {
    return max_right(l, [](S x) { return f(x); });
  }
  template <class F>
  int max_right(int l, F f) const {
    assert(0 <= l && l <= _n);
    assert(f(e()));
    if (l == _n) return _n;
    l += size;
    S sm = e();
    do {
      while (l % 2 == 0) l >>= 1;
      if (!f(op(sm, d[l]))) {
        while (l < size) {
          l = (2 * l);
          if (f(op(sm, d[l]))) {
            sm = op(sm, d[l]);
            l++;
          }
        }
        return l - size;
      }
      sm = op(sm, d[l]);
      l++;
    } while ((l & -l) != l);
    return _n;
  }

  template <bool (*f)(S)>
  int min_left(int r) const {
    return min_left(r, [](S x) { return f(x); });
  }
  template <class F>
  int min_left(int r, F f) const {
    assert(0 <= r && r <= _n);
    assert(f(e()));
    if (r == 0) return 0;
    r += size;
    S sm = e();
    do {
      r--;
      while (r > 1 && (r % 2)) r >>= 1;
      if (!f(op(d[r], sm))) {
        while (r < size) {
          r = (2 * r + 1);
          if (f(op(d[r], sm))) {
            sm = op(d[r], sm);
            r--;
          }
        }
        return r + 1 - size;
      }
      sm = op(d[r], sm);
    } while ((r & -r) != r);
    return 0;
  }

 private:
  int _n, size, log;
  std::vector<S> d;

  void update(int k) { d[k] = op(d[2 * k], d[2 * k + 1]); }
};
#line 2 "graph/tree/LowestCommonAncestor.hpp"
class TreeQuery {
 private:
  struct S {
    int val, id;
  };
  static S op(S a, S b) {
    if (a.val < b.val) {
      return a;
    }
    return b;
  }

  static S e() {
    return {100000000, -1};
  }

  vector<vector<int>> g;
  int n, root;
  int cnt = 0;
  vector<int> st, dep;
  segtree<S, op, e> rmq;

  void build() {
    int time = 0;
    vector<S> v;
    auto dfs = [&](auto& self, int cur, int prev, int d) -> void {
      st[cur] = time++;
      dep[cur] = d;
      v.emplace_back(d, cur);
      for (auto nex : g[cur]) {
        if (nex == prev) continue;
        self(self, nex, cur, d + 1);
        v.emplace_back(d, cur);
        time++;
      }
    };
    dfs(dfs, root, -1, 0);
    rmq = segtree<S, op, e>(v);
  }

 public:
  TreeQuery(int n, int root = 0) : n(n), root(root) {
    g.resize(n);
    st.resize(n);
    dep.resize(n);
  }

  void add_edge(int u, int v) {
    assert(cnt < n - 1);
    g[u].emplace_back(v);
    g[v].emplace_back(u);
    if (++cnt == n - 1) build();
  }

  int lca(int u, int v) {
    int l = st[u];
    int r = st[v];
    if (l > r) swap(l, r);
    return rmq.prod(l, r + 1).id;
  }

  int dist(int u, int v) {
    return dep[u] + dep[v] - 2 * dep[lca(u, v)];
  }

  bool contains(int u, int v, int x) {
    return dist(u, x) + dist(x, v) == dist(u, v);
  }
};
#line 4 "verify/LibraryChecker/tree/LowestCommonAncestor2.test.cpp"

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int n, q;
  in(n, q);
  TreeQuery t(n);
  rep(i, 1, n) {
    int p;
    in(p);
    t.add_edge(i, p);
  }
  rep(i, q) {
    int u, v;
    in(u, v);
    out(t.lca(u, v));
  }
}
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