test/verify/yosupo-lca-4.test.cpp

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Last update: 2026-08-10 11:00:59+00:00
Problem: https://judge.yosupo.jp/problem/lca

Depends on

Code

// clang-format off
// competitive-verifier: PROBLEM https://judge.yosupo.jp/problem/lca
// clang-format on

#include <cstdio>
#include <utility>
#include <vector>

#include "../../graph/tree/offline-lca.hpp"
#include "../../other/printer.hpp"
#include "../../other/scanner.hpp"

using namespace std;

int main() {
  Scanner in(stdin);
  Printer out(stdout);
  int N, Q;
  in.read(N, Q);
  Graph<int> g(N);
  for (int i = 1; i < N; i++) {
    int x;
    in.read(x);
    g.add_directed_edge(x, i);
  }
  vector<pair<int, int>> qs(Q);
  for (auto& [l, r] : qs) in.read(l, r);
  auto ans = offline_lca(g, qs);
  for (auto& p : ans) out.writeln(p);
}

#line 1 "test/verify/yosupo-lca-4.test.cpp"
// clang-format off
// competitive-verifier: PROBLEM https://judge.yosupo.jp/problem/lca
// clang-format on

#include <cstdio>
#include <utility>
#include <vector>

#line 2 "graph/tree/offline-lca.hpp"

#line 5 "graph/tree/offline-lca.hpp"

#line 2 "structure/union-find/union-find.hpp"

#include <algorithm>
#include <cstddef>
#line 7 "structure/union-find/union-find.hpp"

struct UnionFind {
  std::vector<int> data;

  UnionFind() = default;

  explicit UnionFind(std::size_t sz) : data(sz, -1) {}

  bool unite(int x, int y) {
    x = find(x), y = find(y);
    if (x == y) return false;
    if (data[x] > data[y]) std::swap(x, y);
    data[x] += data[y];
    data[y] = x;
    return true;
  }

  int find(int k) {
    if (data[k] < 0) return (k);
    return data[k] = find(data[k]);
  }

  int size(int k) { return -data[find(k)]; }

  bool same(int x, int y) { return find(x) == find(y); }

  std::vector<std::vector<int>> groups() {
    int n = (int)data.size();
    std::vector<std::vector<int>> ret(n);
    for (int i = 0; i < n; i++) {
      ret[find(i)].emplace_back(i);
    }
    ret.erase(
        std::remove_if(ret.begin(), ret.end(),
                       [&](const std::vector<int>& v) { return v.empty(); }),
        ret.end());
    return ret;
  }
};
#line 2 "graph/graph-template.hpp"

#line 4 "graph/graph-template.hpp"
#include <iostream>
#line 6 "graph/graph-template.hpp"

template <typename T = int>
struct Edge {
  int from, to;
  T cost;
  int idx;

  Edge() = default;

  Edge(int from, int to, T cost = 1, int idx = -1)
      : from(from), to(to), cost(cost), idx(idx) {}

  operator int() const { return to; }
};

template <typename T = int>
struct Graph {
  std::vector<std::vector<Edge<T> > > g;
  int es;

  Graph() = default;

  explicit Graph(int n) : g(n), es(0) {}

  std::size_t size() const { return g.size(); }

  void add_directed_edge(int from, int to, T cost = 1) {
    g[from].emplace_back(from, to, cost, es++);
  }

  void add_edge(int from, int to, T cost = 1) {
    g[from].emplace_back(from, to, cost, es);
    g[to].emplace_back(to, from, cost, es++);
  }

  void read(int M, int padding = -1, bool weighted = false,
            bool directed = false) {
    for (int i = 0; i < M; i++) {
      int a, b;
      std::cin >> a >> b;
      a += padding;
      b += padding;
      T c = T(1);
      if (weighted) std::cin >> c;
      if (directed)
        add_directed_edge(a, b, c);
      else
        add_edge(a, b, c);
    }
  }

  inline std::vector<Edge<T> >& operator[](const int& k) { return g[k]; }

  inline const std::vector<Edge<T> >& operator[](const int& k) const {
    return g[k];
  }
};

template <typename T = int>
using Edges = std::vector<Edge<T> >;
#line 8 "graph/tree/offline-lca.hpp"

/**
 * @brief Offline LCA(オフライン最小共通祖先)
 **/
template <typename T>
std::vector<int> offline_lca(const Graph<T>& g,
                             std::vector<std::pair<int, int> >& qs,
                             int root = 0) {
  int n = (int)g.size();
  UnionFind uf(n);
  std::vector<int> st(n), mark(n), ptr(n), ans(qs.size(), -1);
  int top = 0;
  st[top] = root;
  for (auto& [l, r] : qs) mark[l]++, mark[r]++;
  std::vector<std::vector<std::pair<int, int> > > q(n);
  for (int i = 0; i < n; i++) {
    q[i].reserve(mark[i]);
    mark[i] = -1;
    ptr[i] = (int)g[i].size();
  }
  for (int i = 0; i < qs.size(); i++) {
    q[qs[i].first].emplace_back(qs[i].second, i);
    q[qs[i].second].emplace_back(qs[i].first, i);
  }
  auto run = [&](int u) -> bool {
    while (ptr[u]) {
      int v = g[u][--ptr[u]];
      if (mark[v] == -1) {
        st[++top] = v;
        return true;
      }
    }
    return false;
  };
  while (~top) {
    int u = st[top];
    if (mark[u] == -1) {
      mark[u] = u;
    } else {
      uf.unite(u, g[u][ptr[u]]);
      mark[uf.find(u)] = u;
    }
    if (not run(u)) {
      for (auto& [v, i] : q[u]) {
        if (~mark[v] and ans[i] == -1) {
          ans[i] = mark[uf.find(v)];
        }
      }
      --top;
    }
  }
  return ans;
}
#line 2 "other/printer.hpp"

#include <charconv>
#line 6 "other/printer.hpp"
#include <string>
#include <type_traits>
#line 9 "other/printer.hpp"

/**
 * @brief Printer(高速出力)
 */
struct Printer {
 public:
  explicit Printer(FILE* fp) : fp(fp) {}

  ~Printer() { flush(); }

  template <bool f = false, typename T, typename... E>
  void write(const T& t, const E&... e) {
    if (f) write_single(' ');
    write_single(t);
    write<true>(e...);
  }

  template <typename... T>
  void writeln(const T&... t) {
    write(t...);
    write_single('\n');
  }

  void flush() {
    fwrite(line, 1, st - line, fp);
    st = line;
  }

 private:
  FILE* fp = nullptr;
  static constexpr std::size_t line_size = 1 << 16;
  static constexpr std::size_t int_digits = 20;
  char line[line_size + 1] = {};
  char* st = line;

  template <bool f = false>
  void write() {}

  void write_single(const char& t) {
    if (st + 1 >= line + line_size) flush();
    *st++ = t;
  }

  template <typename T, std::enable_if_t<std::is_integral<T>::value, int> = 0>
  void write_single(T s) {
    if (st + int_digits >= line + line_size) flush();
    st += std::to_chars(st, st + int_digits, s).ptr - st;
  }

  void write_single(const std::string& s) {
    for (auto& c : s) write_single(c);
  }

  void write_single(const char* s) {
    while (*s != 0) write_single(*s++);
  }

  template <typename T>
  void write_single(const std::vector<T>& s) {
    for (std::size_t i = 0; i < s.size(); i++) {
      if (i) write_single(' ');
      write_single(s[i]);
    }
  }
};
#line 2 "other/scanner.hpp"

#line 5 "other/scanner.hpp"
#include <cstring>
#line 9 "other/scanner.hpp"

/**
 * @brief Scanner(高速入力)
 */
struct Scanner {
 public:
  explicit Scanner(std::FILE* fp) : fp(fp) {}

  template <typename T, typename... E>
  void read(T& t, E&... e) {
    read_single(t);
    read(e...);
  }

 private:
  static constexpr std::size_t line_size = 1 << 16;
  static constexpr std::size_t int_digits = 20;
  char line[line_size + 1] = {};
  std::FILE* fp = nullptr;
  char* st = line;
  char* ed = line;

  void read() {}

  static inline bool is_space(char c) { return c <= ' '; }

  void reread() {
    std::ptrdiff_t len = ed - st;
    std::memmove(line, st, len);
    char* tmp = line + len;
    ed = tmp + std::fread(tmp, 1, line_size - len, fp);
    *ed = 0;
    st = line;
  }

  void skip_space() {
    while (true) {
      if (st == ed) reread();
      while (*st && is_space(*st)) ++st;
      if (st != ed) return;
    }
  }

  template <typename T, std::enable_if_t<std::is_integral<T>::value, int> = 0>
  void read_single(T& s) {
    skip_space();
    if (st + int_digits >= ed) reread();
    bool neg = false;
    if (std::is_signed<T>::value && *st == '-') {
      neg = true;
      ++st;
    }
    typename std::make_unsigned<T>::type y = *st++ - '0';
    while (*st >= '0') {
      y = 10 * y + *st++ - '0';
    }
    s = (neg ? -y : y);
  }

  template <typename T,
            std::enable_if_t<std::is_same<T, std::string>::value, int> = 0>
  void read_single(T& s) {
    s = "";
    skip_space();
    while (true) {
      char* base = st;
      while (*st && !is_space(*st)) ++st;
      s += std::string(base, st);
      if (st != ed) return;
      reread();
    }
  }

  template <typename T>
  void read_single(std::vector<T>& s) {
    for (auto& d : s) read(d);
  }
};
#line 12 "test/verify/yosupo-lca-4.test.cpp"

using namespace std;

int main() {
  Scanner in(stdin);
  Printer out(stdout);
  int N, Q;
  in.read(N, Q);
  Graph<int> g(N);
  for (int i = 1; i < N; i++) {
    int x;
    in.read(x);
    g.add_directed_edge(x, i);
  }
  vector<pair<int, int>> qs(Q);
  for (auto& [l, r] : qs) in.read(l, r);
  auto ans = offline_lca(g, qs);
  for (auto& p : ans) out.writeln(p);
}

Test cases

Env	Name	Status	Elapsed	Memory
g++	almost_line_00	AC	139 ms	68 MB
g++	almost_line_01	AC	148 ms	68 MB
g++	binary_00	AC	237 ms	67 MB
g++	binary_01	AC	233 ms	67 MB
g++	binary_02	AC	242 ms	67 MB
g++	example_00	AC	2 ms	4 MB
g++	line_00	AC	85 ms	57 MB
g++	line_01	AC	97 ms	65 MB
g++	line_02	AC	37 ms	19 MB
g++	line_03	AC	44 ms	45 MB
g++	line_04	AC	43 ms	35 MB
g++	max_line_00	AC	107 ms	71 MB
g++	max_line_01	AC	119 ms	71 MB
g++	max_line_02	AC	108 ms	71 MB
g++	max_random_00	AC	235 ms	68 MB
g++	max_random_01	AC	240 ms	68 MB
g++	max_random_02	AC	259 ms	68 MB
g++	path_graph_root_centroid_00	AC	98 ms	71 MB
g++	path_graph_root_centroid_01	AC	98 ms	71 MB
g++	path_graph_root_centroid_02	AC	98 ms	71 MB
g++	random_00	AC	179 ms	54 MB
g++	random_01	AC	217 ms	62 MB
g++	random_02	AC	40 ms	19 MB
g++	random_03	AC	108 ms	43 MB
g++	random_04	AC	78 ms	33 MB
clang++	almost_line_00	AC	159 ms	68 MB
clang++	almost_line_01	AC	161 ms	69 MB
clang++	binary_00	AC	271 ms	67 MB
clang++	binary_01	AC	273 ms	67 MB
clang++	binary_02	AC	267 ms	67 MB
clang++	example_00	AC	2 ms	4 MB
clang++	line_00	AC	101 ms	56 MB
clang++	line_01	AC	113 ms	64 MB
clang++	line_02	AC	50 ms	19 MB
clang++	line_03	AC	50 ms	45 MB
clang++	line_04	AC	49 ms	35 MB
clang++	max_line_00	AC	131 ms	71 MB
clang++	max_line_01	AC	128 ms	71 MB
clang++	max_line_02	AC	127 ms	71 MB
clang++	max_random_00	AC	279 ms	68 MB
clang++	max_random_01	AC	271 ms	68 MB
clang++	max_random_02	AC	266 ms	68 MB
clang++	path_graph_root_centroid_00	AC	121 ms	71 MB
clang++	path_graph_root_centroid_01	AC	119 ms	71 MB
clang++	path_graph_root_centroid_02	AC	123 ms	71 MB
clang++	random_00	AC	199 ms	54 MB
clang++	random_01	AC	238 ms	62 MB
clang++	random_02	AC	57 ms	19 MB
clang++	random_03	AC	121 ms	43 MB
clang++	random_04	AC	85 ms	33 MB