跟你犯了同样的错误，顺带帮你改改
- 拓扑```int v = adj[u][i];```改为adj2
- 拓扑```for(int i = 1;i <= n;i ++)```中n改为scccount
```cpp
#include <iostream>
#include <queue>
#include <stack>
#include <vector>
using namespace std;
int n, m;
int a[100005];
vector<int> adj[100005];
vector<int> adj2[100005];
stack<int> st;
int pre[100005];
int low[100005];
int sccNo[100005];
int dscc[100005];
int dis[100005];
int ind[100005];
int scccount = 0;
int dfsTime = 0;
// 缩点
void tarjan(int u) {
pre[u] = low[u] = ++dfsTime;
st.push(u);
for (int i = 0; i < adj[u].size(); i++) {
int v = adj[u][i];
if (!pre[v]) {
tarjan(v);
low[u] = min(low[u], low[v]);
} else if (!sccNo[v]) {
low[u] = min(low[u], pre[v]);
}
}
if (low[u] == pre[u]) {
sccNo[u] = ++scccount;
dscc[scccount] = a[u];
while (true) {
if (st.empty())
break;
if (st.top() == u)
break;
int f = st.top();
sccNo[f] = scccount;
dscc[scccount] += a[f];
st.pop();
}
st.pop();
}
}
void toposort() {
queue<int> q;
for (int i = 1; i <= scccount; i++) {
if (ind[i] == 0) {
dis[i] = dscc[i];
q.push(i);
}
}
while (!q.empty()) {
int u = q.front();
q.pop();
for (int i = 0; i < (int)adj2[u].size(); i++) {
int v = adj2[u][i];
dis[v] = max(dis[v], dis[u] + dscc[v]);
ind[v]--;
if (!ind[v])
q.push(v);
}
}
}
int main() {
cin >> n >> m;
for (int i = 1; i <= n; i++)
cin >> a[i];
while (m--) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
}
for (int i = 1; i <= n; i++) {
if (!pre[i]) {
dfsTime = 0;
tarjan(i);
}
}
for (int i = 1; i <= n; i++) {
for (int j = 0; j < (int)adj[i].size(); j++) {
int g = adj[i][j];
if (sccNo[i] != sccNo[g]) {
adj2[sccNo[i]].push_back(sccNo[g]);
ind[sccNo[g]]++;
}
}
}
// 变为有向无环图
toposort();
int ans = -10000000;
for (int i = 1; i <= n; i++) {
ans = max(ans, dis[i]);
}
cout << ans << endl;
return 0;
}
```
by Q__A__Q @ 2023-06-28 23:42:19
@[Patron_Saint](/user/635780) re是因为m的最大值为1e5，所以vector建图的时候要开1e5以上而不是和点的个数n一样
by Q__A__Q @ 2023-06-28 23:43:59