Topological Sort using Inorder and Iterative methodology

class Solution
{
  public:
    vector<int> findOrder(int n, int m, vector<vector<int>> pre) 
    {
        vector<int>ans;
        vector<int>indeg(n,0);
        vector<int>adj[n];
        queue<int>q;
        for(auto a:pre){
            adj[a[1]].push_back(a[0]);
            indeg[a[0]]++;
        }
        for(int i = 0; i < n; ++ i){
            if(indeg[i] == 0){
                q.push(i);
            }
        }
        while(!q.empty()){
            int cur = q.front();
            q.pop();
            ans.push_back(cur);
            for(auto a:adj[cur]){
                indeg[a]--;
                if(indeg[a] == 0){
                    q.push(a);
                }
            }
        }
        if(ans.size () == n){
            return ans;
        }
        return {};
        //code here
    }
};