WA on #1 #2 #3 #10 #11 搞不明白了（）

#include <iostream>
#include <cstdio>
#include <queue>
using namespace std;
typedef long long ll;

const int maxn = 5e5 + 5;
const int maxm = 5e5 + 5;

struct edge {
    int to, nxt;
} e[maxm], E[maxm];

int tot = 1, head[maxn];
void add(int u, int v) {
    e[++tot].to = v;
    e[tot].nxt = head[u];
    head[u] = tot;
}

int TOT = 1, HEAD[maxn];
void ADD(int U, int V) {
    E[++TOT].to = V;
    E[TOT].nxt = HEAD[U];
    HEAD[U] = TOT;
}

int n, m, s, cnt, top, dfncnt;
int dfn[maxn], low[maxn], stk[maxn];
int a[maxn], scc[maxn], in[maxn];
ll ans, dis[maxn];
bool vis[maxn];

void getscc(int u) {
    low[u] = dfn[u] = ++dfncnt;
    stk[++top] = u;
    vis[u] = true;
    for(int i = head[u]; i; i = e[i].nxt) {
        int v = e[i].to;
        if(!dfn[v]) { getscc(v); low[u] = min(low[u], low[v]); }
        else if(vis[v]) low[u] = min(low[u], low[v]);
    }
    vis[u] = false;
    if(dfn[u] == low[u]) {
        int v;
        while((v = stk[top--])) {
            scc[v] = u;
            if(u == v) break;
            a[u] += a[v];
        }
    }
}

void toposort() {
    queue<int> q;
    q.push(scc[s]);
    dis[scc[s]] = a[scc[s]];
    while(!q.empty()) {
        int u = q.front(); q.pop();
        for(int i = HEAD[u]; i; i = E[i].nxt) {
            int v = E[i].to;
            in[v]--;
            dis[v] = max(dis[v], dis[u] + a[v]);
            if(!in[v]) q.push(v);
        }
    }
}

int main() {
    scanf("%d %d", &n, &m);
    for(int i = 1, u, v; i <= m; i++) {
        scanf("%d %d", &u, &v);
        add(u, v);
    }
    for(int i = 1; i <= n; i++)
        scanf("%d", &a[i]);
    scanf("%d", &s);

    getscc(s);
    for(int i = 1; i <= n; i++)
        for(int j = head[i]; j; j = e[j].nxt) {
            if(!scc[i] || !scc[e[j].to] || scc[i] == scc[e[j].to]) continue;
            ADD(scc[i], scc[e[j].to]);
            in[scc[e[j].to]]++;
        }
    toposort();

    int q, x;
    scanf("%d", &q);
    for(int i = 1; i <= q; i++) {
        scanf("%d", &x);
        ans = max(ans, dis[scc[x]]);
    }
    printf("%lld\n", ans);
    return 0;
}