Tarjon悬2关代码求调

#include<bits/stdc++.h>
using namespace std;
const int N = 5e5+5;
const int M = 2e6+5;
int head[N],nxt[M<<1],to[M<<1];
int dfn[N],low[N];
bool vis[N],vvis[N];
vector<int> ans[N];
int cnt_ans = 0;
int tot = 0,cnt = 0,root;
void add(int x,int y){
    nxt[++tot] = head[x];
    to[tot] = y;
    head[x] = tot;

    nxt[++tot] = head[y];
    to[tot] = x;
    head[y] = tot;
}
void tarjon(int x,int last_edge){
    dfn[x] = low[x] = ++cnt;
    for(int i=head[x];i;i=nxt[i]){
        int y = to[i];
        if(!dfn[y]){
            tarjon(y,i);
            low[x] = min(low[x],low[y]);
            if(low[y] > dfn[x]){
                printf("%d %d\n",x,y);
                vis[i] = true;
                vis[i^1] = true;
            }
        }else if(i != (last_edge^1)){
            low[x] = min(low[x],dfn[y]);
        }
    }
}
void dfs(int x){
    ans[cnt_ans].push_back(x);
    for(int i=head[x];i;i=nxt[i]){
        int y = to[i];
        if(vis[i] || vvis[y]){
            continue;
        }
        vvis[y] = true;
        dfs(y);
    }
}
int main(){
    int n,m;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++){
        int x,y;
        scanf("%d%d",&x,&y);
        add(x,y);
    }
    for(int i=1;i<=n;i++){
        if(!dfn[i]){
            root = i;
            tarjon(i,-1);
        }
    }
    for(int i=1;i<=n;i++){
        if(!vvis[i]){
            cnt_ans ++;
            vvis[i] = true;
            dfs(i);
        }
    }
    printf("%d\n",cnt_ans);
    for(int i=1;i<=cnt_ans;i++){
        printf("%d ",ans[i].size());
        for(int j=0;j<ans[i].size();j++){
            printf("%d ",ans[i][j]);
        }
        puts("");
    }
}