强连通分量tarjan

#include<iostream>//强连通分量tarjan
#include<cstdio>
#include<algorithm>
#include<queue>
#include<cstring>
using namespace std;
#define maxn 400010
#define INF 1e18
int low[maxn],dfn[maxn],sta[maxn],d[maxn]/*value*/,dis[maxn]/*total value*/,fa[maxn];/*enumerate*/
int ne[maxn],u[maxn],v[maxn],fi[maxn];
int f[maxn];
bool omit[maxn];
int n,m,t,top,times,tot;
int ans;
void edge(int x,int y)
{
	t++;
	ne[t]=fi[x];
	fi[x]=t;
	u[t]=x;
	v[t]=y;
}

void scc(int now)//strongly connectly component
{
	times++;
	dfn[now]=low[now]=times;
	top++;
	sta[top]=now;
	omit[now]=0;
	for (int i=fi[now];i!=-1;i=ne[i])
	{
		if (!dfn[v[i]])
		{
			scc(v[i]);
			low[now]=min(low[now],low[v[i]]);
		}
		else if (!omit[v[i]])
		{
			if (dfn[v[i]]<low[now]) low[now]=dfn[v[i]];
		}
	}
	if (low[now]==dfn[now])
	{
		tot++;
		do
		{		
			dis[tot]+=d[sta[top]];
			fa[sta[top]]=tot; 
			omit[sta[top]]=1;
			top--;
		}
		while (sta[top+1]!=now);
	}
}
int main()
{

	scanf("%d%d",&n,&m);
	for (int i=1;i<=n;i++) scanf("%d",&d[i]);
	
	t=-1;
	top=0;
	tot=0;
	times=0;
	memset(dis,0,sizeof(dis));	
	memset(dfn,0,sizeof(dfn));
	memset(num,0,sizeof(num));
	for (int i=1;i<=n;i++) fi[i]=-1;
	for (int i=1;i<=m;i++)
	{
		int x,y;
		scanf("%d%d",&x,&y);
		edge(x,y);
	}
	for (int i=1;i<=n;i++) 
		if (!dfn[i]) scc(i);
		

	return 0;
}