This documentation is automatically generated by online-judge-tools/verification-helper
#define PROBLEM "https://judge.yosupo.jp/problem/two_edge_connected_components"
#include "../default/t.cpp"
#include "../graph/ECC.cpp"
signed main() {
ios::sync_with_stdio(false), cin.tie(NULL);
int n, m; cin >> n >> m;
vector<array<int, 2>> e(m);
for(auto &[u, v] : e) cin >> u >> v;
ECC ecc(e, n);
cout << ecc.size << '\n';
for(int g = 0; g < ecc.size; g++) {
auto gv = ecc.vertexGroup(g);
cout << ssize(gv);
for(int x : gv) cout << ' ' << x;
cout << '\n';
}
return 0;
}
#line 1 "test/two_edge_connected_components.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/two_edge_connected_components"
#line 1 "default/t.cpp"
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfenv>
#include <cfloat>
#include <chrono>
#include <cinttypes>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdarg>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <streambuf>
#include <string>
#include <tuple>
#include <type_traits>
#include <variant>
#include <bit>
#include <compare>
#include <concepts>
#include <numbers>
#include <ranges>
#include <span>
#define INT128_MAX (__int128)(((unsigned __int128) 1 << ((sizeof(__int128) * __CHAR_BIT__) - 1)) - 1)
#define INT128_MIN (-INT128_MAX - 1)
#define clock chrono::steady_clock::now().time_since_epoch().count()
using namespace std;
template<class T1, class T2>
ostream& operator<<(ostream& os, const pair<T1, T2> pr) {
return os << pr.first << ' ' << pr.second;
}
template<class T, size_t N>
ostream& operator<<(ostream& os, const array<T, N> &arr) {
for(size_t i = 0; T x : arr) {
os << x;
if (++i != N) os << ' ';
}
return os;
}
template<class T>
ostream& operator<<(ostream& os, const vector<T> &vec) {
for(size_t i = 0; T x : vec) {
os << x;
if (++i != size(vec)) os << ' ';
}
return os;
}
template<class T>
ostream& operator<<(ostream& os, const set<T> &s) {
for(size_t i = 0; T x : s) {
os << x;
if (++i != size(s)) os << ' ';
}
return os;
}
template<class T1, class T2>
ostream& operator<<(ostream& os, const map<T1, T2> &m) {
for(size_t i = 0; pair<T1, T2> x : m) {
os << x;
if (++i != size(m)) os << ' ';
}
return os;
}
#ifdef DEBUG
#define dbg(...) cerr << '(', _do(#__VA_ARGS__), cerr << ") = ", _do2(__VA_ARGS__)
template<typename T> void _do(T &&x) { cerr << x; }
template<typename T, typename ...S> void _do(T &&x, S&&...y) { cerr << x << ", "; _do(y...); }
template<typename T> void _do2(T &&x) { cerr << x << endl; }
template<typename T, typename ...S> void _do2(T &&x, S&&...y) { cerr << x << ", "; _do2(y...); }
#else
#define dbg(...)
#endif
using ll = long long;
using ull = unsigned long long;
using ldb = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template<typename T> using min_heap = priority_queue<T, vector<T>, greater<T>>;
template<typename T> using max_heap = priority_queue<T>;
template<ranges::forward_range rng, class T = ranges::range_value_t<rng>, class OP = plus<T>>
void pSum(rng &v) {
if (!v.empty())
for(T p = v[0]; T &x : v | views::drop(1))
x = p = OP()(p, x);
}
template<ranges::forward_range rng, class T = ranges::range_value_t<rng>, class OP>
void pSum(rng &v, OP op) {
if (!v.empty())
for(T p = v[0]; T &x : v | views::drop(1))
x = p = op(p, x);
}
template<ranges::forward_range rng>
void Unique(rng &v) {
ranges::sort(v);
v.resize(unique(v.begin(), v.end()) - v.begin());
}
template<ranges::random_access_range rng>
rng invPerm(rng p) {
rng ret = p;
for(int i = 0; i < ssize(p); i++)
ret[p[i]] = i;
return ret;
}
template<ranges::random_access_range rng, ranges::random_access_range rng2>
rng Permute(rng v, rng2 p) {
rng ret = v;
for(int i = 0; i < ssize(p); i++)
ret[p[i]] = v[i];
return ret;
}
template<bool directed>
vector<vector<int>> readGraph(int n, int m, int base) {
vector<vector<int>> g(n);
for(int i = 0; i < m; i++) {
int u, v; cin >> u >> v;
u -= base, v -= base;
g[u].emplace_back(v);
if constexpr (!directed)
g[v].emplace_back(u);
}
return g;
}
template<class T>
void setBit(T &msk, int bit, bool x) {
msk = (msk & ~(T(1) << bit)) | (T(x) << bit);
}
template<class T> void flipBit(T &msk, int bit) { msk ^= T(1) << bit; }
template<class T> bool getBit(T msk, int bit) { return msk >> bit & T(1); }
template<class T>
T floorDiv(T a, T b) {
if (b < 0) a *= -1, b *= -1;
return a >= 0 ? a / b : (a - b + 1) / b;
}
template<class T>
T ceilDiv(T a, T b) {
if (b < 0) a *= -1, b *= -1;
return a >= 0 ? (a + b - 1) / b : a / b;
}
template<class T> bool chmin(T &a, T b) { return a > b ? a = b, 1 : 0; }
template<class T> bool chmax(T &a, T b) { return a < b ? a = b, 1 : 0; }
#line 1 "graph/ECC.cpp"
struct ECC {
vector<int> vb, gv, vid;
vector<array<int, 2>> e;
int size = -1;
ECC(vector<array<int, 2>> &_e, int n) : vid(n), e(_e) {
auto newComp = [&]() { vb.emplace_back(ssize(gv)), size++; };
vector<vector<int>> g(n);
for(int i = 0; auto [u, v] : e) {
g[u].emplace_back(i);
g[v].emplace_back(i++);
}
int t = 0, root;
vector<int> tin(n, -1), low(n), s;
vector<bool> vis(ssize(e), false);
auto extract = [&](int v) {
newComp();
do {
int u = s.back(); s.pop_back();
vid[u] = size;
gv.emplace_back(u);
} while(gv.back() != v);
};
auto dfs = [&](int v, auto &&self) -> void {
tin[v] = low[v] = t++;
s.emplace_back(v);
for(int i : g[v]) if (!vis[i]) {
int x = e[i][0] ^ e[i][1] ^ v;
vis[i] = true;
if (tin[x] != -1) {
low[v] = min(low[v], tin[x]);
} else {
self(x, self);
low[v] = min(low[v], low[x]);
if (low[x] > tin[v]) extract(x);
}
}
if (v == root) extract(root);
};
for(int v = 0; v < n; v++)
if (tin[v] == -1)
dfs(root = v, dfs);
newComp();
}
vector<int> vertexGroup(int id) {
return {gv.begin() + vb[id], gv.begin() + vb[id + 1]};
}
bool isBridge(int id) { return vid[e[id][0]] != vid[e[id][1]]; }
vector<vector<int>> bridgeTree() {
vector<vector<int>> g(size);
for(auto [u, v] : e) {
if ((u = vid[u]) != (v = vid[v])) {
g[u].emplace_back(v);
g[v].emplace_back(u);
}
}
return g;
}
};
#line 5 "test/two_edge_connected_components.test.cpp"
signed main() {
ios::sync_with_stdio(false), cin.tie(NULL);
int n, m; cin >> n >> m;
vector<array<int, 2>> e(m);
for(auto &[u, v] : e) cin >> u >> v;
ECC ecc(e, n);
cout << ecc.size << '\n';
for(int g = 0; g < ecc.size; g++) {
auto gv = ecc.vertexGroup(g);
cout << ssize(gv);
for(int x : gv) cout << ' ' << x;
cout << '\n';
}
return 0;
}