Floyd

代码说明：

  从任意一条单边路径开始。所有两点之间的距离是边的权，或者无穷大，如果两点之间没有边相连。 　　2，对于每一对顶点 u 和 v，看看是否存在一个顶点 w 使得从 u 到 w 再到 v 比己知的路径更短。如果是更新它。 　　3，不可思议的是，只要按排适当，就能得到结果。(A unilateral path from any start. All the distance between two points is the right side, or infinity, if there is no edge between two points connected. 2, for each pair of vertices u and v, to see if there is a vertex w from u to w and then to make than the known path v shorter. If you are updating it. 3, incredibly, just press the appropriate row, you can get results.)