Tarjan + spfa，但跟题解区的这个思路相同的代码比较后，感觉差不多 Link

My code:

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=5e5+5;
vector<int>g[N];
vector<int>ne[N],nw[N];
int cnt,idx,n,m,s,p;
int dfn[N],low[N],scc[N],a[N],b[N],dis[N],jzh[N],in[N];
bool vis[N];
bool fw[N];
stack<int>t;
void dfs(int x){
	dfn[x]=++cnt;
	low[x]=dfn[x];
	t.push(x);vis[x]=1;
	for(auto v:g[x]){
		if(!dfn[v])	dfs(v),low[x]=min(low[x],low[v]);
		else if(vis[v])	low[x]=min(low[x],dfn[v]);
	}
	if(low[x]==dfn[x]){
		++idx;
		while(1){
			auto ts=t.top();t.pop();
			vis[ts]=0;
			scc[ts]=idx;
			jzh[idx]+=a[ts];
			if(ts==x)break;
		}
	}
}
void spfa(){
	memset(dis,-0x3f,sizeof(dis));
	queue<int>q;
	vis[scc[s]]=1,dis[scc[s]]=0;
	q.push(scc[s]);
	while(q.size()){
		auto u=q.front();q.pop();
		vis[u]=0;
		for(int i=0;i<ne[u].size();i++){
			int v=ne[u][i],w=nw[u][i];
			if(dis[v]<dis[u]+w){
				dis[v]=dis[u]+w;
				if(!vis[v])q.push(v),vis[v]=1;
			}
		}
	}
	int sum=0;
	for(int i=1;i<=p;i++)sum=max(sum,dis[scc[b[i]]]+idx);
	cout<<sum;
}
signed main(){
	cin>>n>>m;
	while(m--){
		int u,v;
		cin>>u>>v;
		g[u].push_back(v);
	}
	for(int i=1;i<=n;i++)cin>>a[i];
	cin>>s>>p;
	for(int i=1;i<=p;i++)cin>>b[i];
	
	for(int i=1;i<=n;i++)if(!dfn[i])dfs(i);
	
	for(int i=1;i<=n;i++){
		for(int v:g[i]){
			if(scc[i]!=scc[v]){
				ne[scc[i]+idx].push_back(scc[v]),in[scc[v]]++;
				nw[scc[i]+idx].push_back(0);
			}
		}
	}
	for(int i=1;i<=idx;i++){
		ne[i].push_back(i+idx);
		nw[i].push_back(jzh[i]);
	}
	spfa();
	return 0;
}