说明：  Dandn文件给出了输入参数的名称及格式 即在调用prim前先输入邻接矩阵D和节点个数n 输入prim 得到两行的矩阵T,将上下两行数字对应的节点相连即可
(The Dandn file gives the name and format of the input parameter That is, before entering prim, the adjacency matrix D and the number of nodes n are input Input prim Get the matrix T of the two row, and connect the nodes corresponding to the two lines of the upper and lower rows)