访问所有节点的最短路径

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class Solution {
 public:
  int shortestPathLength(vector<vector<int>>& graph) {
    int n = graph.size();
    queue<tuple<int, int, int>> q;
    vector<vector<int>> seen(n, vector<int>(1 << n));
    for (int i = 0; i < n; i++) {
      q.emplace(i, 1 << i, 0);
      seen[i][1 << i] = true;
    }
    int ans = 0;
    while (q.size()) {
      auto [u, mask, dist] = q.front();
      q.pop();
      if (mask == (1 << n) - 1) {
        ans = dist;
        break;
      }
      for (int v : graph[u]) {
        int mask_v = mask | (1 << v);
        if (!seen[v][mask_v]) {
          q.emplace(v, mask_v, dist + 1);
          seen[v][mask_v] = true;
        }
      }
    }
    return ans;
  }
};