verify/aoj_grl3b.cpp

• View this file on GitHub
• Last update: 2026-03-06 21:32:29+09:00
• Problem: http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_3_B

Depends on

• graph/lowlink.hpp
• templates/alias.hpp
• templates/macro.hpp

Code

#define PROBLEM                                                                \
  "http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_3_B"

#include <bits/stdc++.h>
using namespace std;
#include "graph/lowlink.hpp"
#include "templates/alias.hpp"
#include "templates/macro.hpp"

int main() {
  ll N, M;
  in(N, M);
  VC<VC<int>> G(N);
  rep(_, M) {
    int a, b;
    in(a, b);
    G[a].emplace_back(b), G[b].emplace_back(a);
  }

  LowLink LG(G);
  sort(all(LG.bridges));

  set<pii> S;

  for (auto [a, b] : LG.bridges) {
    if (a > b)
      swap(a, b);
    S.emplace(a, b);
  }

  for (auto [a, b] : S)
    out(a, b);
}

#line 1 "verify/aoj_grl3b.cpp"
#define PROBLEM                                                                \
  "http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_3_B"

#include <bits/stdc++.h>
using namespace std;
#line 4 "templates/macro.hpp"

// 引数の長さで内容が変わるrep 参考: https://trap.jp/post/1224
#define overload4(a, b, c, d, ...) d
#define _rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep(...) overload4(__VA_ARGS__, REP, _rep)(__VA_ARGS__)
#define _rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define RREP(i, a, b) for (int i = (int)(b - 1); i >= (int)(a); i--)
#define rrep(...) overload4(__VA_ARGS__, RREP, _rrep)(__VA_ARGS__)

#define all(a) (a).begin(), (a).end()

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

template <typename T1, typename T2>
std::istream &operator>>(std::istream &is, std::pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}

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

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

// pythonのprintライクな関数 参考:
// https://nyaannyaan.github.io/library/template/inout.hpp
inline void out() { std::cout << std::endl; }
template <typename T, typename... U, char sep = ' '>
void out(const T &t, const U &...u) {
  std::cout << t;

  if (sizeof...(u))
    std::cout << sep;

  out(u...);
}

// cinの短縮関数 参考: https://nyaannyaan.github.io/library/template/inout.hpp
inline void in() {}
template <typename T, class... U> void in(T &t, U &...u) {
  std::cin >> t;
  in(u...);
}

template <typename T> inline T ceil_div(T a, T b) { return (a + b - 1) / b; }
template <typename T> inline T mod_pow(T a, T n, T mod) {
  T res = 1;
  while (n) {
    if (n % 2 != 0) {
      res *= a;
      res %= mod;
    }

    a *= a;
    a %= mod;

    n >>= 1;
  }

  return res;
}
template <typename T> inline T minus_mod(T a, T b) { return ((a % b) + b) % b; }

template <typename T> void apply_vec(std::vector<T> &v, T (*fn)(T)) {
  for (int i = 0; i < v.size(); i++)
    v[i] = fn(v[i]);
}
#line 4 "graph/lowlink.hpp"

// 参考: https://algo-logic.info/bridge-lowlink/
struct LowLink {
  std::vector<int> ord, low, parents, articulation_points;
  std::vector<std::vector<int>> G;
  std::vector<bool> used;
  std::vector<std::pair<int, int>> bridges;
  LowLink(const std::vector<std::vector<int>> &_G) : G(_G) {
    ord.resize(_G.size(), 0), low.resize(_G.size(), 0),
        used.resize(_G.size(), false), parents.resize(_G.size(), -1);
    int d = 0;
    rep(i, _G.size()) {
      if (!used[i])
        d = dfs(i, d, -1);
    }
  }

  int dfs(int cur, int d, int par = -1) {
    used[cur] = true, ord[cur] = low[cur] = d++, parents[cur] = par;
    bool is_articulation_point = false;
    int child_cnt = 0;

    for (const auto &nxt : G[cur]) {
      if (!used[nxt]) {
        child_cnt++, d = dfs(nxt, d, cur);
        chmin(low[cur], low[nxt]);
        if (par != -1 && ord[cur] <= low[nxt])
          is_articulation_point = true;
        if (ord[cur] < low[nxt])
          bridges.emplace_back(cur, nxt);
      } else if (nxt != par) {
        chmin(low[cur], ord[nxt]);
      }
    }

    if (par == -1 && child_cnt >= 2)
      is_articulation_point = true;
    if (is_articulation_point)
      articulation_points.emplace_back(cur);

    return d;
  }
};
#line 7 "templates/alias.hpp"

template <class T> using VC = std::vector<T>;
template <class T>
using rpriority_queue = std::priority_queue<T, VC<T>, std::greater<T>>;
using ll = long long;
using ld = long double;
using pii = std::pair<ll, ll>;
using vi = VC<ll>;
using vvi = VC<vi>;
using vvvi = VC<vvi>;
using vb = VC<bool>;
using vvb = VC<vb>;
using vf = VC<double>;
using vvf = VC<vf>;
using vpii = VC<pii>;
using vvpii = VC<vpii>;
using si = std::set<ll>;
using spii = std::set<pii>;
using mii = std::map<ll, ll>;
const std::string upperlist = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const std::string lowerlist = "abcdefghijklmnopqrstuvwxyz";
#define mp make_pair
#define dms << " " <<

constexpr int MOD998 = 998244353;
#line 9 "verify/aoj_grl3b.cpp"

int main() {
  ll N, M;
  in(N, M);
  VC<VC<int>> G(N);
  rep(_, M) {
    int a, b;
    in(a, b);
    G[a].emplace_back(b), G[b].emplace_back(a);
  }

  LowLink LG(G);
  sort(all(LG.bridges));

  set<pii> S;

  for (auto [a, b] : LG.bridges) {
    if (a > b)
      swap(a, b);
    S.emplace(a, b);
  }

  for (auto [a, b] : S)
    out(a, b);
}

Test cases

Env	Name	Status	Elapsed	Memory
g++	00_small_00	AC	2 ms	4 MB
g++	00_small_01	AC	2 ms	4 MB
g++	00_small_02	AC	2 ms	4 MB
g++	00_small_03	AC	2 ms	4 MB
g++	00_small_04	AC	2 ms	4 MB
g++	00_small_05	AC	2 ms	4 MB
g++	01_critical_00	AC	2 ms	4 MB
g++	01_critical_01	AC	2 ms	4 MB
g++	01_critical_02	AC	2 ms	4 MB
g++	01_critical_03	AC	2 ms	4 MB
g++	01_critical_04	AC	2 ms	4 MB
g++	01_critical_05	AC	2 ms	4 MB
g++	01_critical_06	AC	2 ms	4 MB
g++	01_critical_07	AC	2 ms	4 MB
g++	01_critical_08	AC	2 ms	4 MB
g++	01_critical_09	AC	2 ms	4 MB
g++	01_critical_10	AC	2 ms	4 MB
g++	01_critical_11	AC	2 ms	4 MB
g++	01_critical_12	AC	2 ms	4 MB
g++	02_grid_00	AC	2 ms	4 MB
g++	02_grid_01	AC	2 ms	4 MB
g++	02_grid_02	AC	2 ms	4 MB
g++	03_rand_00	AC	2 ms	4 MB
g++	03_rand_01	AC	2 ms	4 MB
g++	03_rand_02	AC	2 ms	4 MB
g++	03_rand_03	AC	2 ms	4 MB
g++	03_rand_04	AC	2 ms	4 MB
g++	03_rand_05	AC	2 ms	4 MB
g++	03_rand_06	AC	2 ms	4 MB
g++	03_rand_07	AC	2 ms	4 MB
g++	03_rand_08	AC	3 ms	4 MB
g++	03_rand_09	AC	3 ms	4 MB
g++	03_rand_10	AC	3 ms	4 MB
g++	03_rand_11	AC	5 ms	4 MB
g++	04_linear_00	AC	2 ms	4 MB
g++	04_linear_01	AC	3 ms	4 MB
g++	04_linear_02	AC	8 ms	6 MB
g++	04_linear_03	AC	8 ms	6 MB
g++	05_maximum_00	AC	18 ms	6 MB
g++	05_maximum_01	AC	23 ms	6 MB
clang++	00_small_00	AC	2 ms	4 MB
clang++	00_small_01	AC	2 ms	4 MB
clang++	00_small_02	AC	2 ms	4 MB
clang++	00_small_03	AC	2 ms	4 MB
clang++	00_small_04	AC	2 ms	4 MB
clang++	00_small_05	AC	2 ms	4 MB
clang++	01_critical_00	AC	2 ms	4 MB
clang++	01_critical_01	AC	2 ms	4 MB
clang++	01_critical_02	AC	2 ms	4 MB
clang++	01_critical_03	AC	2 ms	4 MB
clang++	01_critical_04	AC	2 ms	4 MB
clang++	01_critical_05	AC	2 ms	4 MB
clang++	01_critical_06	AC	2 ms	4 MB
clang++	01_critical_07	AC	2 ms	4 MB
clang++	01_critical_08	AC	2 ms	4 MB
clang++	01_critical_09	AC	2 ms	4 MB
clang++	01_critical_10	AC	2 ms	4 MB
clang++	01_critical_11	AC	2 ms	4 MB
clang++	01_critical_12	AC	2 ms	4 MB
clang++	02_grid_00	AC	2 ms	4 MB
clang++	02_grid_01	AC	2 ms	4 MB
clang++	02_grid_02	AC	2 ms	4 MB
clang++	03_rand_00	AC	2 ms	4 MB
clang++	03_rand_01	AC	2 ms	4 MB
clang++	03_rand_02	AC	2 ms	4 MB
clang++	03_rand_03	AC	2 ms	4 MB
clang++	03_rand_04	AC	2 ms	4 MB
clang++	03_rand_05	AC	2 ms	4 MB
clang++	03_rand_06	AC	2 ms	4 MB
clang++	03_rand_07	AC	2 ms	4 MB
clang++	03_rand_08	AC	3 ms	4 MB
clang++	03_rand_09	AC	3 ms	4 MB
clang++	03_rand_10	AC	3 ms	4 MB
clang++	03_rand_11	AC	5 ms	4 MB
clang++	04_linear_00	AC	3 ms	4 MB
clang++	04_linear_01	AC	3 ms	4 MB
clang++	04_linear_02	AC	8 ms	5 MB
clang++	04_linear_03	AC	8 ms	5 MB
clang++	05_maximum_00	AC	18 ms	5 MB
clang++	05_maximum_01	AC	23 ms	6 MB

Back to top page