You can reverse the topological sort instead

If you don't want to create two adjacency lists you can use Tarjan's algorithm instead, which finds SCCs with just one DFS.

Build double edges and mark if its reserved edge or not, look at this:

define a graph:
vector<pair<int, int> > adj[MAXN];

addedge u->v:
adj[u].push_back(make_pair(v, 0))
adj[v].push_back(make_pair(u, 1))

go through edges from u:
for(auto v : adj[u]) {
  if(v.second == 0) {
    //original edge
  } else {
    //reserved edge
  }
}

or you can build two graphs:

define:
vector<int> org[MAXN], rev[MAXN];

addedge u->v
org[u].push_back(u);
rev[v].push_back(v);

go through original edges out of u:
for(int v : org[u]) {

}

go through reversed edges out of u:
for(int v : rev[u]) {

}