0847.cpp

class Solution {
public:
    int shortestPathLength(vector<vector<int>>& graph) {
        const int n = graph.size();
        const int goal = (1 << n) - 1;
        queue<pair<int, int>> q;
        vector<vector<int>> visited(n, vector<int>(1 << n));

        for (int i = 0; i < graph.size(); i++) q.push({i, 1 << i});

        int ans = 0;
        while (!q.empty()) {
            int s = q.size();
            while (s--) {
                auto p = q.front();
                q.pop();
                int node = p.first;
                int state = p.second;
                if (state == goal) return ans;
                if (visited[node][state]) continue;
                visited[node][state] = 1;
                for (int next : graph[node])
                    q.push({next, state | (1 << next)});
            }
            ans++;
        }

        return -1;
    }
};