void floyd(int n, int dist[][MAXN]) {
    for (int k = 0; k < n; k++)
        for (int i = 0; i < n; i++)
            for (int j = 0; j < n; j++)
                if (__________) // 在此处填入选项
                    dist[i][j] = dist[i][k] + dist[k][j];
}