tarjan板子
有一个小地方注意，第一个最大的强连通分量一定是字典序最小的，因为搜索的时候是从小到大的
代码：
#include <bits/stdc++.h>
#define int long long
#define sc(a) scanf("%lld",&a)
#define scc(a,b) scanf("%lld %lld",&a,&b)
#define sccc(a,b,c) scanf("%lld %lld %lld",&a,&b,&c)
#define scs(a) scanf("%s",a)
#define schar(a) scanf("%c",&a)
#define pr(a) printf("%lld",a)
#define fo(i,a,b) for(int i=a;i<b;++i)
#define re(i,a,b) for(int i=a;i<=b;++i)
#define rfo(i,a,b) for(int i=a;i>b;--i)
#define rre(i,a,b) for(int i=a;i>=b;--i)
#define prn() printf("\n")
#define prs() printf(" ")
#define mkp make_pair
#define pii pair<int,int>
#define pub(a) push_back(a)
#define pob() pop_back()
#define puf(a) push_front(a)
#define pof() pop_front()
#define fst first
#define snd second
#define frt front()
#define bak back()
#define mem0(a) memset(a,0,sizeof(a))
#define memmx(a) memset(a,0x3f3f,sizeof(a))
#define memmn(a) memset(a,-0x3f3f,sizeof(a))
#define debug
#define db double
#define yyes cout<<"YES"<<endl;
#define nno cout<<"NO"<<endl;
#define all(i,a) for(auto i=a.begin();i!=a.end();++i)
using namespace std;
typedef vector<int> vei;
typedef vector<pii> vep;
typedef map<int,int> mpii;
typedef map<char,int> mpci;
typedef map<string,int> mpsi;
typedef deque<int> deqi;
typedef deque<char> deqc;
typedef priority_queue<int> mxpq;
typedef priority_queue<int,vector<int>,greater<int> > mnpq;
typedef priority_queue<pii> mxpqii;
typedef priority_queue<pii,vector<pii>,greater<pii> > mnpqii;
const int maxn=500005;
const int inf=0x3f3f3f3f3f3f3f3f;
const int MOD=100000007;
const db eps=1e-10;
const db pi=3.1415926535;
int qpow(int a,int b){int tmp=a%MOD,ans=1;while(b){if(b&1){ans*=tmp,ans%=MOD;}tmp*=tmp,tmp%=MOD,b>>=1;}return ans;}
int lowbit(int x){return x&-x;}
int max(int a,int b){return a>b?a:b;}
int min(int a,int b){return a<b?a:b;}
int mmax(int a,int b,int c){return max(a,max(b,c));}
int mmin(int a,int b,int c){return min(a,min(b,c));}
void mod(int &a){a+=MOD;a%=MOD;}
bool chk(int now){}
int half(int l,int r){while(l<=r){int m=(l+r)/2;if(chk(m))r=m-1;else l=m+1;}return l;}
int ll(int p){return p<<1;}
int rr(int p){return p<<1|1;}
int mm(int l,int r){return (l+r)/2;}
int lg(int x){if(x==0) return 1;return (int)log2(x)+1;}
bool smleql(db a,db b){if(a<b||fabs(a-b)<=eps)return true;return false;}
bool bigeql(db a,db b){if(a>b||fabs(a-b)<=eps)return true;return false;}
bool eql(db a,db b){if(fabs(a-b)<eps) return 1;return 0;}
db len(db a,db b,db c,db d){return sqrt((a-c)*(a-c)+(b-d)*(b-d));}
bool isp(int x){if(x==1)return false;if(x==2)return true;for(int i=2;i*i<=x;++i)if(x%i==0)return false;return true;}
inline int read(){
char ch=getchar();int s=0,w=1;
while(ch<48||ch>57){if(ch=='-')w=-1;ch=getchar();}
while(ch>=48&&ch<=57){s=(s<<1)+(s<<3)+ch-48;ch=getchar();}
return s*w;
}
inline void write(int x){
if(x<0)putchar('-'),x=-x;
if(x>9)write(x/10);
putchar(x%10+48);
}
int gcd(int a, int b){
if(a==0) return b;
if(b==0) return a;
if(!(a&1)&&!(b&1)) return gcd(a>>1,b>>1)<<1;
else if(!(b&1)) return gcd(a,b>>1);
else if(!(a&1)) return gcd(a>>1,b);
else return gcd(abs(a-b),min(a,b));
}
int lcm(int x,int y){return x*y/gcd(x,y);}
int n,m,a,b,cc;
vei e[maxn],scc[maxn];
int c[maxn],tot=0;
int dfn[maxn],low[maxn],timer=0;
stack<int> s;
bool vis[maxn];
void tarjan(int x){
dfn[x]=low[x]=++timer;
s.push(x);
vis[x]=1;
for(auto y:e[x]){
if(!dfn[y]){
tarjan(y);
low[x]=min(low[x],low[y]);
}
else if(vis[y]) low[x]=min(low[x],dfn[y]);
}
if(low[x]==dfn[x]){
++tot;
while(s.top()!=x){
int t=s.top();
c[t]=tot;
scc[tot].pub(t);
vis[t]=0;
s.pop();
}
c[s.top()]=tot;
scc[tot].pub(s.top());
vis[s.top()]=0;
s.pop();
}
}
int mx=-inf,p=-1;
bool ok(vei a,vei b){
fo(i,0,a.size())
if(a[i]>b[i]) return 1;
else if(a[i]<b[i]) return 0;
return 0;
}
signed main(){
cin>>n>>m;
re(i,1,m){
cin>>a>>b>>cc;
if(cc==1) e[a].pub(b);
else e[a].pub(b),e[b].pub(a);
}
re(i,1,n) if(!dfn[i]) tarjan(i);
re(i,1,tot) sort(scc[i].begin(),scc[i].end());
re(i,1,tot){
if((int)scc[i].size()>mx){
mx=max(mx,(int)scc[i].size());
p=i;
}
}
assert(mx>0);
cout<<mx<<endl;
for(auto i:scc[p]) cout<<i<<' ';
return 0;
}