需要在某个城市n个居民小区之间铺设煤气管道，则在这n个居民小区之间只需要铺设n-1条管道即可。假设任意两个小区之间都可以铺设管道，但由于地理环境不同，所需要的费用也不尽相同。选择最优的方案能使总投资尽可能小，这个问题即为求无向网的最小生成树。-Need to be in a particular city n laying between gas in residential area, is between the n dweller you just need to lay n- 1 the pipes.Assuming that laying pipes can be between any two communities, but due to the geographical environment is different, need cost are also different.Choose the optimal scheme can make the total investment is as small as possible, the problem is the minimum spanning tree of undirected network.