tests/graph/cycle/libchecker-undirected.test.cpp

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Last update: 2025-08-17 00:21:01+09:00
Problem: https://judge.yosupo.jp/problem/cycle_detection_undirected

Depends on

Code

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

#include "../../../library/fastio.hpp"
#include "../../../library/graph/cycle.hpp"
#define PROBLEM "https://judge.yosupo.jp/problem/cycle_detection_undirected"

int main() {
  int n, m;
  asalib::FastIO >> n >> m;
  vector<pair<int, int>> edges(m);
  rep(i, m) {
    int u, v;
    asalib::FastIO >> u >> v;
    edges[i] = { u, v };
  }
  auto cycle = asalib::graph::cycle(n, edges, false);
  if (cycle) {
    auto [vs, es] = *cycle;
    asalib::FastIO << es.size() << '\n';
    rep(i, vs.size()) asalib::FastIO << vs[i] << " \n"[i == vs.size() - 1];
    rep(i, es.size()) asalib::FastIO << es[i] << " \n"[i == es.size() - 1];
  }
  else {
    asalib::FastIO << -1 << '\n';
  }
  return 0;
}

#line 1 "tests/graph/cycle/libchecker-undirected.test.cpp"
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

#line 2 "library/fastio.hpp"

#line 5 "library/fastio.hpp"
#include <concepts>
#line 11 "library/fastio.hpp"
#include <type_traits>
using namespace std;

// TODO: 何も入力がない場合にも対応する？

namespace asalib {
  namespace _internal {
    class FastIO {
      private:
      using uint = unsigned int;
      static constexpr uint BUFFER_SIZE = 1 << 20;
      static constexpr uint MAX_TOKEN_SIZE = 64;

      // ===== Read ===== //

      private:
      array<char, BUFFER_SIZE> read_buffer;
      array<char, BUFFER_SIZE>::iterator read_ptr;
      uint read_size = 0;

      void load() {
        // まだ読んでないデータを前に持ってくる
        memcpy(read_buffer.begin(), read_ptr, read_size - (read_ptr - read_buffer.begin()));
        read_size -= read_ptr - read_buffer.begin();
        read_ptr = read_buffer.begin();
        // stdin から読み込み
        read_size += fread(read_buffer.begin() + read_size, 1, BUFFER_SIZE - read_size, stdin);
      }

      void skip_space() {
        // 制御文字 + space
        // DEL (127 = 0x7F) がコーナーケースだがまあ使わんやろ
        while (*read_ptr <= ' ') ++read_ptr;
      }

      template<typename T>
        requires(integral<T> || is_same_v<T, __int128_t> || is_same_v<T, __uint128_t>)
      void _read_uint(T& x) {
        x = 0;
        while (true) {
          uint64_t v;
          memcpy(&v, read_ptr, 8);
          // '0' -> 0 処理
          // こっちを先にやることで制御文字系もはじく
          v -= 0x30'30'30'30'30'30'30'30;
          // ASCII 範囲外
          if (v & 0x80'80'80'80'80'80'80'80) break;
          // 桁ごとの数字から数値に
          v = (v * 10 + (v >> 8)) & 0x00ff00ff00ff00ff;
          v = (v * 100 + (v >> 16)) & 0x0000ffff0000ffff;
          v = (v * 10000 + (v >> 32)) & 0x00000000ffffffff;
          x = 1'0000'0000 * x + v;
          read_ptr += 8;
        }
        while (true) {
          uint32_t v;
          memcpy(&v, read_ptr, 4);
          v -= 0x30'30'30'30;
          if (v & 0x80'80'80'80) break;
          v = (v * 10 + (v >> 8)) & 0x00ff00ff;
          v = (v * 100 + (v >> 16)) & 0x0000ffff;
          x = 1'0000 * x + v;
          read_ptr += 4;
        }
        while (true) {
          uint16_t v;
          memcpy(&v, read_ptr, 2);
          v -= 0x3030;
          if (v & 0x8080) break;
          v = (v * 10 + (v >> 8)) & 0x00ff;
          x = 100 * x + v;
          read_ptr += 2;
        }
        if (*read_ptr > ' ') x = 10 * x + (*read_ptr++ & 0x0f);
      }

      void read_commonop() {
        // そろそろ限界なら読み込み
        if ((read_ptr - read_buffer.begin()) + MAX_TOKEN_SIZE >= BUFFER_SIZE) load();
        skip_space();
      }

      public:
      FastIO& operator>>(char& x) {
        read_commonop();
        x = *read_ptr++;
        return *this;
      }

      FastIO& operator>>(string& x) {
        read_commonop();
        x.clear();
        while (*read_ptr > ' ') {
          x += *read_ptr++;
          if (read_ptr == read_buffer.end()) load();
        }
        return *this;
      }

      template<typename T>
        requires(integral<T> || is_same_v<T, __int128_t> || is_same_v<T, __uint128_t>)
      FastIO& operator>>(T& x) {
        read_commonop();
        if constexpr (is_signed_v<T> || is_same_v<T, __int128_t>) {
          if (*read_ptr == '-') {
            ++read_ptr;
            _read_uint(x);
            x = -x;
            return *this;
          }
        }
        _read_uint(x);
        return *this;
      }

      // ===== Write ===== //

      private:
      array<char, BUFFER_SIZE> write_buffer;
      array<char, BUFFER_SIZE>::iterator write_ptr;
      static constexpr uint MAX_PRECOMPUTE_NUM = 1'0000;
      static constexpr uint MAX_PRECOMPUTE_NUM_DIGIT = 4;

      static constexpr array<char, MAX_PRECOMPUTE_NUM * MAX_PRECOMPUTE_NUM_DIGIT> digits = [] {
        array<char, MAX_PRECOMPUTE_NUM * MAX_PRECOMPUTE_NUM_DIGIT> digits {};
        for (uint i = 0; i < MAX_PRECOMPUTE_NUM; ++i) {
          uint x = i;
          for (int j = MAX_PRECOMPUTE_NUM_DIGIT - 1; j >= 0; --j) {
            digits[i * MAX_PRECOMPUTE_NUM_DIGIT + j] = '0' + (x % 10);
            x /= 10;
          }
        }
        return digits;
      }();

      template<typename T>
        requires(integral<T> || is_same_v<T, __int128_t> || is_same_v<T, __uint128_t>)
      static constexpr array<T, numeric_limits<T>::digits10 + 1> Pow10 = [] {
        array<T, numeric_limits<T>::digits10 + 1> pow10 {};
        pow10[0] = 1;
        for (uint i = 1; i < pow10.size(); ++i) pow10[i] = pow10[i - 1] * 10;
        return pow10;
      }();

      void write_commonop() {
        // そろそろ限界なら書き込む
        if ((write_ptr - write_buffer.begin()) + MAX_TOKEN_SIZE >= BUFFER_SIZE) flush();
      }

      void putchar(const char& x) { *write_ptr++ = x; }

      template<typename T, int NumDig>
        requires(integral<T> || is_same_v<T, __int128_t> || is_same_v<T, __uint128_t>)
      void _write_uint_top(const T& x) {
        // leading-zero を書き込まないようにする
        if constexpr (NumDig > 1) {
          if (x < Pow10<T>[NumDig - 1]) {
            _write_uint_top<T, NumDig - 1>(x);
            return;
          }
        }
        copy_n(digits.begin() + (x + 1) * MAX_PRECOMPUTE_NUM_DIGIT - NumDig, NumDig, write_ptr);
        write_ptr += NumDig;
      }

      template<typename T, int NumDig>
        requires(integral<T> || is_same_v<T, __int128_t> || is_same_v<T, __uint128_t>)
      void _write_uint(const T& x) {
        if constexpr (NumDig >= 0) {
          if constexpr (NumDig > MAX_PRECOMPUTE_NUM_DIGIT) _write_uint<T, NumDig - MAX_PRECOMPUTE_NUM_DIGIT>(x / MAX_PRECOMPUTE_NUM);
          copy_n(digits.begin() + x % MAX_PRECOMPUTE_NUM * MAX_PRECOMPUTE_NUM_DIGIT, MAX_PRECOMPUTE_NUM_DIGIT, write_ptr);
          write_ptr += MAX_PRECOMPUTE_NUM_DIGIT;
        }
      }

      template<typename T, int NumDig>
        requires(integral<T> || is_same_v<T, __int128_t> || is_same_v<T, __uint128_t>)
      void _write_uint_root(const T& x) {
        if constexpr (is_same_v<T, __int128_t> || is_same_v<T, __uint128_t>) {
          // 128bit 除算はおそいので 64bit 除算を使う
          if (x < Pow10<T>[16]) {
            _write_uint_root<uint64_t, NumDig>(x);
          }
          else if (x < Pow10<T>[32]) {
            _write_uint_root<uint64_t, NumDig>(x / Pow10<T>[16]);
            _write_uint<uint64_t, 16>(x % Pow10<T>[16]);
          }
          else {
            _write_uint_root<uint64_t, NumDig>(x / Pow10<T>[32]);
            _write_uint<uint64_t, 16>(x % Pow10<T>[32] / Pow10<T>[16]);
            _write_uint<uint64_t, 16>(x % Pow10<T>[16]);
          }
          return;
        }

        if constexpr (NumDig < numeric_limits<T>::digits10) {
          if (x >= Pow10<T>[NumDig]) {
            _write_uint_root<T, NumDig + MAX_PRECOMPUTE_NUM_DIGIT>(x);
            return;
          }
        }
        _write_uint_top<T, MAX_PRECOMPUTE_NUM_DIGIT>(x / Pow10<T>[NumDig - MAX_PRECOMPUTE_NUM_DIGIT]);
        if constexpr (NumDig > MAX_PRECOMPUTE_NUM_DIGIT) _write_uint<T, NumDig - MAX_PRECOMPUTE_NUM_DIGIT>(x % Pow10<T>[NumDig - MAX_PRECOMPUTE_NUM_DIGIT]);
      }

      public:
      void flush() {
        fwrite(write_buffer.begin(), 1, write_ptr - write_buffer.begin(), stdout);
        write_ptr = write_buffer.begin();
      }

      FastIO& operator<<(const char& x) {
        write_commonop();
        putchar(x);
        return *this;
      }

      FastIO& operator<<(const string& x) {
        write_commonop();
        uint idx = 0;
        while (idx < x.size()) {
          const uint siz = min(BUFFER_SIZE - static_cast<uint>(write_ptr - write_buffer.begin()), static_cast<uint>(x.size()) - idx);
          copy_n(x.begin() + idx, siz, write_ptr);
          write_ptr += siz;
          idx += siz;
          if (write_ptr == write_buffer.end()) flush();
        }
        return *this;
      }

      template<typename T>
        requires(integral<T> || is_same_v<T, __int128_t> || is_same_v<T, __uint128_t>)
      FastIO& operator<<(const T& x) {
        write_commonop();
        if constexpr (is_signed_v<T> || is_same_v<T, __int128_t>) {
          if (x < 0) {
            putchar('-');
            _write_uint_root<T, MAX_PRECOMPUTE_NUM_DIGIT>(-x);
            return *this;
          }
        }
        _write_uint_root<T, MAX_PRECOMPUTE_NUM_DIGIT>(x);
        return *this;
      }

      // ===== Common ====== //

      public:
      FastIO() {
        read_ptr = read_buffer.begin();
        write_ptr = write_buffer.begin();
        load();
      }

      ~FastIO() { flush(); }
    };
  }  // namespace _internal

  inline _internal::FastIO FastIO;
}  // namespace asalib
#line 2 "library/graph/cycle.hpp"

#line 6 "library/graph/cycle.hpp"
#include <optional>
#line 10 "library/graph/cycle.hpp"
using namespace std;

#line 2 "library/_internal/graph-base.hpp"

#line 5 "library/_internal/graph-base.hpp"
#include <ranges>
#line 7 "library/_internal/graph-base.hpp"
using namespace std;

namespace asalib::_internal {
  // vector<vector<int>> とかの隣接リストを表す型
  template<class T>
  concept adjacency_list = requires(T t) {
    { t.size() } -> convertible_to<size_t>;
    { t[0] } -> ranges::range;
    { *ranges::begin(t[0]) } -> convertible_to<size_t>;
  };

  // 辺のリストを表す型
  // 重み付きも考慮し pair<int, int> と tuple<int, int, int> の両方を許容
  template<class T>
  concept edge_list = requires(T t) {
    { t.size() } -> convertible_to<size_t>;
    { get<0>(t[0]) } -> convertible_to<size_t>;
    { get<1>(t[0]) } -> convertible_to<size_t>;
  };
}  // namespace asalib::_internal
#line 13 "library/graph/cycle.hpp"

namespace asalib::graph {
  template<_internal::edge_list T>
  optional<pair<vector<size_t>, vector<size_t>>> cycle(const size_t n_vertex, const T& edgelist, const bool is_directed = false) {
    vector adj_list(n_vertex, vector<pair<size_t, size_t>>());
    rep(i, edgelist.size()) {
      size_t u = get<0>(edgelist[i]), v = get<1>(edgelist[i]);
      assert(u < n_vertex);
      assert(v < n_vertex);
      adj_list[u].emplace_back(v, i);
      if (!is_directed) adj_list[v].emplace_back(u, i);
    }

    vector visited(n_vertex, false);
    vector finished(n_vertex, false);
    vector<bool> used(edgelist.size(), false);
    stack<size_t> st;
    size_t base_point = -1;

    function<bool(size_t)> dfs = [&](const size_t v) -> bool {
      visited[v] = true;
      for (auto [to, edge_id] : adj_list[v]) {
        if (used[edge_id]) continue;
        used[edge_id] = true;
        st.emplace(edge_id);
        if (!finished[to] && visited[to]) {
          base_point = to;
          return true;
        }
        if (!visited[to] && dfs(to)) return true;
        st.pop();
        used[edge_id] = false;
      }
      finished[v] = true;
      return false;
    };

    for (size_t i = 0; i < n_vertex; ++i) {
      if (!visited[i]) {
        if (dfs(i)) {
          size_t v = base_point;
          vector<size_t> edges, verts;
          while (!st.empty()) {
            size_t edge_id = st.top();
            st.pop();
            edges.emplace_back(edge_id);
            if (is_directed) {
              assert(edgelist[edge_id].second == v);
              v = edgelist[edge_id].first;
            }
            else {
              assert(edgelist[edge_id].first == v || edgelist[edge_id].second == v);
              v = (edgelist[edge_id].first == v ? edgelist[edge_id].second : edgelist[edge_id].first);
            }
            verts.emplace_back(v);
            if (v == base_point) break;
          }
          ranges::reverse(verts);
          ranges::reverse(edges);
          assert(verts.size() == edges.size());
          assert(verts[0] == base_point);
          return make_pair(verts, edges);
        }
      }
    }
    return nullopt;
  }
}  // namespace asalib::graph
#line 9 "tests/graph/cycle/libchecker-undirected.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/cycle_detection_undirected"

int main() {
  int n, m;
  asalib::FastIO >> n >> m;
  vector<pair<int, int>> edges(m);
  rep(i, m) {
    int u, v;
    asalib::FastIO >> u >> v;
    edges[i] = { u, v };
  }
  auto cycle = asalib::graph::cycle(n, edges, false);
  if (cycle) {
    auto [vs, es] = *cycle;
    asalib::FastIO << es.size() << '\n';
    rep(i, vs.size()) asalib::FastIO << vs[i] << " \n"[i == vs.size() - 1];
    rep(i, es.size()) asalib::FastIO << es[i] << " \n"[i == es.size() - 1];
  }
  else {
    asalib::FastIO << -1 << '\n';
  }
  return 0;
}