[TOEFL] tarjan+拓扑排序+bitset优化

• n<=30000,m<=60000

Code

#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
using namespace std;
const int N=3e4+100;
struct node{int y,n;}e[N<<1],E[N<<1];
int lin[N<<1],LIN[N<<1],dfn[N],inv[N],du[N],c[N],low[N],cnt=0,tot=0,len=0,LEN=0,n,m,x,y;
void read(int x,int y,node *e,int *lin,int &len){
	e[++len].y=y,e[len].n=lin[x],lin[x]=len;
}
bitset<N> f[N];
stack<int> S;
queue<int> q;
void tarjan(int x){
	dfn[x]=low[x]=++tot;inv[x]=1,S.push(x);
	for(int i=lin[x];i;i=e[i].n){
		int y=e[i].y;
		if(!dfn[y]){
			tarjan(y);
			low[x]=min(low[x],low[y]);
		}else if(inv[y]) low[x]=min(low[x],dfn[y]);
	}
	if(dfn[x]==low[x]){
		int now=0;
		cnt++;
		while(now!=x){
			now=S.top();S.pop();inv[now]=0;
			f[cnt][now]=1;
			c[now]=cnt;
		}
	}
}
int main()
{
	freopen("toefl.in","r",stdin);
	freopen("toefl.out","w",stdout);
	scanf("%d%d",&n,&m);
	rep(i,1,m){
		scanf("%d%d",&x,&y);
		read(x,y,e,lin,len);
	}
	rep(i,1,n)if(!dfn[i])tarjan(i);
	rep(x,1,n){
		for(int i=lin[x];i;i=e[i].n){
			int y=e[i].y;
			if(c[x]==c[y])continue;
			read(c[y],c[x],E,LIN,LEN),du[c[x]]++;
		}
	}
	rep(i,1,cnt){
		if(!du[i]){
			q.push(i);
		}
	}
	while(q.size()){
		int x=q.front();q.pop();
		for(int i=LIN[x];i;i=E[i].n){
			int y=E[i].y;
			du[y]--;
			f[y]|=f[x];
			if(!du[y])q.push(y);
		}
	}
	rep(i,1,n){
		printf("%d\n",f[c[i]].count());
	}return 0;
}