LeetCode: Shortest Path Visiting All Nodes

class Solution {
public:

    using pi = pair <int, int>;
    using pii = pair <int, pi>;

    int shortestPathLength(vector<vector<int>> &graph){
        int n = graph.size();
        vector <int> g[n];
        for(int u=0;u<=n-1;u++){
            for(auto v: graph[u]){
                g[u].push_back(v);
            }
        }

        int Bit = (1 << n) - 1;
        vector < vector <int> > dis(n, vector <int> (Bit + 1, 1e9));
        vector < vector <bool> > vs(n, vector <bool> (Bit + 1, false));
        queue <pii> q;
        for(int u=0;u<=n-1;u++){
            dis[u][1 << u] = 0;
            q.push({0, {u, 1 << u}});
        }

        while(!q.empty()){
            int d = q.front().first;
            int u = q.front().second.first;
            int bit = q.front().second.second;
            q.pop();
            if(vs[u][bit]) continue; vs[u][bit] = true;
            if(bit == Bit) return d;
            for(auto v: g[u]){
                int nxtbit = bit | (1 << v);
                if(!vs[v][nxtbit] and 1 + d < dis[v][nxtbit]){
                    dis[v][nxtbit] = d + 1;
                    q.push({d + 1, {v, nxtbit}});
                }
            }
        }

        return -1;
    }
};