while(!q.empty())
	{
		u = q.front(), q.pop();
		as = max(as, dp[u]);
		for(int e = hed[u]; e; e = nxt[e])
		{
			v = to[e];
			dp[v] = max(dp[v], dp[u] + (v <= n)); //
			if(!--d[v]) q.push(v);
		}
	}

$WA$ 成 $20pt$

改成

while(!q.empty())
	{
		u = q.front(), q.pop();
		if(u > n) --dp[u]; //
		as = max(as, dp[u]);
		for(int e = hed[u]; e; e = nxt[e])
		{
			v = to[e];
			dp[v] = max(dp[v], dp[u] + 1); //
			if(!--d[v]) q.push(v);
		}
	}

就 $A$ 了