test/yosupo_TECC.test.cpp

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Last update: 2023-07-17 18:02:31+09:00
Problem: https://judge.yosupo.jp/problem/two_edge_connected_components

Depends on

Code

#define PROBLEM "https://judge.yosupo.jp/problem/two_edge_connected_components"

#include "../template.hpp"
#include "../Graph2/TwoEdgeConnectedComponents.hpp"

signed main(){
    int N,M;cin>>N>>M;
    Graph<int> G(N);
    G.read(M,0);

    TwoEdgeConnectedComponents<int> TECC(G);
    cout<<TECC.group.size()<<"\n";
    for(auto &w:TECC.group){
        cout<<w.size();
        for(auto &x:w) cout<<" "<<x;
        cout<<"\n";
    }
    return 0;
}

#line 1 "test/yosupo_TECC.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/two_edge_connected_components"

#line 1 "template.hpp"
#include<bits/stdc++.h>
using namespace std;
#define ALL(x) begin(x),end(x)
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
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>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}

#line 1 "Graph2/GraphTemplate.hpp"



// graph template
// ref : https://ei1333.github.io/library/graph/graph-template.hpp
template<typename T=int>
struct Edge{
    int from,to;
    T w;
    int idx;
    Edge()=default;
    Edge(int from,int to,T w=1,int idx=-1):from(from),to(to),w(w),idx(idx){}
    operator int() const{return to;}
};

template<typename T=int>
struct Graph{
    vector<vector<Edge<T>>> g;
    int V,E;
    Graph()=default;
    Graph(int n):g(n),V(n),E(0){}

    int size(){
        return (int)g.size();
    }
    void resize(int k){
        g.resize(k);
        V=k;
    }
    inline const vector<Edge<T>> &operator[](int k)const{
        return (g.at(k));
    }
    inline vector<Edge<T>> &operator[](int k){
        return (g.at(k));
    }
    void add_directed_edge(int from,int to,T cost=1){
        g[from].emplace_back(from,to,cost,E++);
    }
    void add_edge(int from,int to,T cost=1){
        g[from].emplace_back(from,to,cost,E);
        g[to].emplace_back(to,from,cost,E++);
    }
    void read(int m,int pad=-1,bool weighted=false,bool directed=false){
        for(int i=0;i<m;i++){
            int u,v;cin>>u>>v;
            u+=pad,v+=pad;
            T w=T(1);
            if(weighted) cin>>w;
            if(directed) add_directed_edge(u,v,w);
            else         add_edge(u,v,w);
        }
    }
};


#line 2 "Graph2/LowLink.hpp"

template<typename T>
struct LowLink{
    Graph<T> &g;
    vector<int> ord,low;
    vector<int> art;// articulation (true/false)
    vector<Edge<T>> bridge;

    LowLink(Graph<T> &g):g(g){
        ord.assign(g.V,-1);
        low.assign(g.V,-1);
        art.resize(g.V);

        int idx=0;
        function<void(int,int)> dfs=[&](int pre,int cur){
            ord[cur]=idx++;
            low[cur]=ord[cur];

            int pre_c=0,ch=0;
            bool art_f=false;

            for(auto &e:g[cur]){
                if(e==pre and pre_c==0){
                    pre_c++;
                    continue;
                }
                if(ord[e]<0){
                    ch++;
                    dfs(cur,e);
                    low[cur]=min(low[cur],low[e]);
                    art_f|=(pre>=0 and low[e]>=ord[cur]);
                    if(ord[cur]<low[e]) bridge.push_back(e);
                }
                else{
                    low[cur]=min(low[cur],ord[e]);
                }
            }
            if(pre==-1) art_f|=(ch>1);
            art[cur]=art_f;
            return ;
        };
        for(int i=0;i<g.V;i++)if(ord[i]<0) dfs(-1,i);
    }
};
#line 2 "Graph2/TwoEdgeConnectedComponents.hpp"

/*
二重辺連結成分分解をし，頂点をgroupに分ける
group[i] : グループiが持つ頂点番号
belong[i] : 頂点iが所属するグループ番号
*/
template<typename T>
struct TwoEdgeConnectedComponents{
public:
    LowLink<T> LL;
    void dfs(Graph<T> &g,int pre,int cur,int &k){
        if(pre>=0 and LL.ord[pre]>=LL.low[cur]) belong[cur]=belong[pre];
        else                                    belong[cur]=k++;

        for(auto &e:g[cur])if(belong[e]==-1) dfs(g,cur,e,k);
    }

public:
    vector<int> belong;
    vector<vector<int>> group;
    Graph<T> tree;

    TwoEdgeConnectedComponents(Graph<T> &g):LL(g),belong(g.size(),-1){
        int k=0;
        for(int i=0;i<g.size();i++)if(belong[i]==-1) dfs(g,-1,i,k);
        group.resize(k);
        for(int i=0;i<g.size();i++) group[belong[i]].push_back(i);
        tree=Graph<T>(k);
        for(auto &e:LL.bridge) tree.add_edge(belong[e.from],belong[e.to],e.w);
    }
};
#line 5 "test/yosupo_TECC.test.cpp"

signed main(){
    int N,M;cin>>N>>M;
    Graph<int> G(N);
    G.read(M,0);

    TwoEdgeConnectedComponents<int> TECC(G);
    cout<<TECC.group.size()<<"\n";
    for(auto &w:TECC.group){
        cout<<w.size();
        for(auto &x:w) cout<<" "<<x;
        cout<<"\n";
    }
    return 0;
}