Dictionary<int, List<edge>> [] graph = new Dictionary<int, List<edge>>[40];
只是申请了40个Dictionary<int, List<edge>>
但是每个都没有实例化
Dictionary这种数组系统不能自动实例化的,
int[]之类就可以自动实例化,每个默认值为都为0
要么写成Dictionary<int, List<edge>> [] graph = new Dictionary<int, List<edge>>[40]{...........};
或者第二个for循环之前实例化
graph[j]=new Dictionary<int, List<edge>>;

Dictionary<int, List<edge>> [] graph = new Dictionary<int, List<edge>>[40];
            for (j = 0; j < wavelength; j++)
             {
                graph[j] = new Dictionary<int, List<edge>>(); // 加上这一句
                for (i = 1; i < 29; i++)
                {
                    graph[j].Add(i, new List<edge>());//Object reference not set to an instance of an object
                }

            }

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