<p>There are&nbsp;<code>n</code>&nbsp;items each&nbsp;belonging to zero or one of&nbsp;<code>m</code>&nbsp;groups where <code>group[i]</code>&nbsp;is the group that the <code>i</code>-th item belongs to and it&#39;s equal to <code>-1</code>&nbsp;if the <code>i</code>-th item belongs to no group. The items and the groups are zero indexed. A group can have no item belonging to it.</p>

<p>Return a sorted list of the items such that:</p>

<ul>
	<li>The items that belong to the same group are next to each other in the sorted list.</li>
	<li>There are some&nbsp;relations&nbsp;between these items where&nbsp;<code>beforeItems[i]</code>&nbsp;is a list containing all the items that should come before the&nbsp;<code>i</code>-th item in the sorted array (to the left of the&nbsp;<code>i</code>-th item).</li>
</ul>

<p>Return any solution if there is more than one solution and return an <strong>empty list</strong>&nbsp;if there is no solution.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<p><strong><img alt="" src="https://assets.leetcode.com/uploads/2019/09/11/1359_ex1.png" style="width: 191px; height: 181px;" /></strong></p>

<pre>
<strong>Input:</strong> n = 8, m = 2, group = [-1,-1,1,0,0,1,0,-1], beforeItems = [[],[6],[5],[6],[3,6],[],[],[]]
<strong>Output:</strong> [6,3,4,1,5,2,0,7]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 8, m = 2, group = [-1,-1,1,0,0,1,0,-1], beforeItems = [[],[6],[5],[6],[3],[],[4],[]]
<strong>Output:</strong> []
<strong>Explanation:</strong>&nbsp;This is the same as example 1 except that 4 needs to be before 6 in the sorted list.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= m &lt;= n &lt;= 3 * 10<sup>4</sup></code></li>
	<li><code>group.length == beforeItems.length == n</code></li>
	<li><code>-1 &lt;= group[i] &lt;= m - 1</code></li>
	<li><code>0 &lt;= beforeItems[i].length &lt;= n - 1</code></li>
	<li><code>0 &lt;= beforeItems[i][j] &lt;= n - 1</code></li>
	<li><code>i != beforeItems[i][j]</code></li>
	<li><code>beforeItems[i]&nbsp;</code>does not contain&nbsp;duplicates elements.</li>
</ul>

class Solution {
public:
    vector<int> bfs(queue<int> &q, unordered_map<int, vector<int>>& adj, unordered_map<int, int>& indegree){
        vector<int> ans;
        while(!q.empty()){
            int top = q.front();
            q.pop();

            for(auto nbr: adj[top]){
                indegree[nbr]--;
                if(indegree[nbr] == 0){
                    q.push(nbr);
                }
            }
            ans.push_back(top);
        }
        return ans;
    }

    vector<int> sortItems(int n, int m, vector<int>& group, vector<vector<int>>& beforeItems) {
        for (int i = 0; i < n; i++) {
            if (group[i] == -1) {
                group[i] = m++;
            }
        }
        
       unordered_map<int, vector<int>> itemsAdj;
       unordered_map<int, int> itemsIn;

       for(int i = 0; i < n; i++){
        for(int j = 0; j < beforeItems[i].size(); j++){
            itemsAdj[beforeItems[i][j]].push_back(i);
        }
        itemsIn[i] = beforeItems[i].size();
       } 

       queue<int> q1;
       
       for(auto it: itemsIn){
        if(it.second == 0){
            q1.push(it.first);
        }
       }

       vector<int> itemsOrder = bfs(q1, itemsAdj, itemsIn);
       if(itemsOrder.empty() || itemsOrder.size() != n){
        return {};
       }
    
       cout<<"itemsOrder: "<<endl;
       for(auto it: itemsOrder){
        cout<<it<<", ";
       }
       cout<<endl;

       unordered_map<int, vector<int>> groupsMap;
       for(auto i: itemsOrder){
        int groupOfEl = group[i];
        groupsMap[groupOfEl].push_back(i);
       }

       unordered_map<int, vector<int>> groupsAdj;
       unordered_map<int, int> groupsIn;
       for(int i = 0; i < n; i++){
        for(int j = 0; j < beforeItems[i].size(); j++){
            cout<<"i: "<<i<<" size"<<beforeItems[i].size()<<endl;
            if(group[beforeItems[i][j]] != group[i]){
                groupsAdj[group[beforeItems[i][j]]].push_back(group[i]);
                groupsIn[group[i]]++;
            }
        }
       }

       cout<<"groupsAdj: "<<endl;
       for(auto it: groupsAdj){
        cout<<it.first<<"--> ";
        for(auto i: it.second){
            cout<<i<<", ";
        }
        cout<<endl;
       }
       cout<<endl;
       for(auto it: groupsMap){
        if(!groupsIn.count(it.first)){
            groupsIn[it.first] = 0;
        }
       }
       cout<<"groupsIn: "<<endl;
       for(auto it: groupsIn){
        cout<<it.first<<"-> "<<it.second<<endl;
       }
       cout<<endl;

       

        queue<int> q2;
        
        for(auto it: groupsIn){
            if(it.second == 0){
                q2.push(it.first);
            }
        }
        
        vector<int> groupsOrder = bfs(q2, groupsAdj, groupsIn);
        if(groupsOrder.empty() || groupsOrder.size() != groupsMap.size()){
            return {};
        }
       cout<<"groupsOrder: "<<endl;
       for(auto it: groupsOrder){
        cout<<it<<", ";
       }
       cout<<endl;

        vector<int> res;

        for(auto it: groupsOrder){
            for(auto i: groupsMap[it]){
                res.push_back(i);
            }
        }

        return res;
    }
};
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