正题

题目链接:https://www.luogu.org/problemnew/show/P1726

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题目大意

求最大的强联通分量和包含的点

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解题思路

$tarjan$模板不解释。

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$code$

#include<cstdio>
#include<algorithm>
#include<stack>
using namespace std;
const int N=5010,M=50100;
struct node{int to,next;
}a[2*M];
stack<int> Stack;
int n,m,tot,cnt,num,ans,mark;
int ls[N],dfn[N],low[N],siz[N],in[N];
bool v[N];
void addl(int x,int y)
{a[++tot].to=y;a[tot].next=ls[x];ls[x]=tot;
}
void tarjan(int x)
{Stack.push(x);v[x]=1;dfn[x]=low[x]=++cnt;for(int i=ls[x];i;i=a[i].next){int y=a[i].to;if(!dfn[y]){tarjan(y);low[x]=min(low[x],low[y]);}else if(v[y])low[x]=min(low[x],dfn[y]);}if(low[x]==dfn[x]){++num;while(Stack.top()!=x){int y=Stack.top();Stack.pop();in[y]=num;siz[num]++;v[y]=0;}Stack.pop();v[x]=0;siz[num]++;in[x]=num;}
}
int main()
{scanf("%d%d",&n,&m);for(int i=1;i<=m;i++){int x,y,z;scanf("%d%d%d",&x,&y,&z);addl(x,y);if(z>1) addl(y,x);}for(int i=1;i<=n;i++)if(!dfn[i]) tarjan(i);for(int i=1;i<=n;i++)if(siz[in[i]]>ans){ans=siz[in[i]];mark=in[i];}printf("%d\n",ans);for(int i=1;i<=n;i++)if(in[i]==mark) printf("%d ",i);}