第一次写 Tarjan，它貌似会把两个点都看成强连通分量，然后一建图就会成环，导致无法拓补排序。

#include <bits/stdc++.h>
using namespace std;
#define MAXN 10001

int n, m, u, v, cnt, ssum, ans;
int a[MAXN], sum[MAXN], f[MAXN];
int dfn[MAXN], low[MAXN], scc[MAXN];
int us[MAXN], vs[MAXN], in[MAXN];
vector<int> e[MAXN];
bitset<MAXN> ins;
stack<int> st;
queue<int> que;

void tarjan(int x){
	low[x] = dfn[x] = ++cnt;
	st.push(x);
	for (auto i: e[x]){
		if (!dfn[i]){
			tarjan(i);
			low[x] = min(low[x], low[i]);
		}else if (ins.test(i)){
			low[x] = min(low[x], dfn[i]);
		}
	}
	if (dfn[x] == low[x]){
		scc[x] = ++ssum;
		sum[ssum] = a[x];
		while (st.top() != x){
			scc[st.top()] = ssum;
			ins.reset(st.top());
			sum[ssum] += a[st.top()];
			st.pop();
		}
		st.pop();
		ins.reset(x);
	}
}

void topsort(){
	for (int i(1); i<=ssum; ++i){
		if (!in[i]){
			que.push(i);
			f[i] = sum[i];
		}
	}
	while (!que.empty()){
		u = que.front();
		que.pop();
		
		for (auto v: e[u]){
			f[v] = max(f[v], f[u]+sum[v]);
			if (!(--in[v])) que.push(v);
		}
		ans = max(ans, f[u]);
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	
	cin >> n >> m;
	for (int i(1); i<=n; ++i) cin >> a[i];
	for (int i(1); i<=m; ++i){
		cin >> u >> v;
		us[i] = u;
		vs[i] = v;
		e[u].push_back(v);
	}
	for (int i(1); i<=n; ++i){
		if (!dfn[i]) tarjan(i);
	}
	
	for (int i(1); i<=n; ++i) e[i].clear();
	for (int i(1); i<=m; ++i){
		u = scc[us[i]];
		v = scc[vs[i]];
		if (u != v){
			e[u].push_back(v);
			++in[v];
		}
	}
	topsort();
	cout << ans;
	
	return 0;
}