Topological Sort

stack <int> stk;
int vis[5005], cy;
vector <int> g[5005], order;
map <pii, int> mp;


void toposort(int u){
    if(vis[u]) {
        if(vis[u]==1) cy = true;
        return;
    }
    vis[u] = 1;
    for(int i=0;i<g[u].size();i++){
        toposort(g[u][i]);
    }
    stk.push(u);
    vis[u] = 2;
}

void inittoposort(int n){
    cy = false;
    memset(vis, false, sizeof vis);
    for(int i=1;i<=n;i++){
        if(!vis[i]){
            toposort(i);
        }
    }
    while(!stk.empty()){
        order.push_back(stk.top());
        //cout << stk.top() << " ";
        stk.pop();
    }
}