1298

class Solution {
public:
    int maxCandies(vector<int>& status, vector<int>& candies, vector<vector<int>>& keys, vector<vector<int>>& containedBoxes, vector<int>& initialBoxes) {
        vector<bool> explored(status.size(), false);
        vector<bool> visited(status.size(), false);
        int ans = 0;
        queue<int> q;

        // Input the starting boxes in queue.
        for(int box: initialBoxes){
            if(status[box]){
                q.push(box);
                visited[box] = true;
            }
            else
                explored[box] = true;
        }

        // Pop from queue and input next boxes in queue.
        while(!q.empty()){
            int box = q.front(); q.pop();
            ans += candies[box];
            // Input boxes which are explored and their keys are found.
            for(int key: keys[box]){
                status[key] = 1;
                if(explored[key] && !visited[key]){
                    q.push(key);
                    visited[key] = true;
                }
            }
            // Input or explored next boxes based on keys.
            for(int nextBox: containedBoxes[box]){
                if(status[nextBox] && !visited[nextBox]){
                    q.push(nextBox);
                    visited[nextBox] = true;
                }
                else
                    explored[nextBox] = true;
            }
        }
        return ans;
    }
};