在secshortest中我希望只得到一条次短路,结果却出来好几条，因此在使用时，要得到次短路，只能用roadcost()函数分别求一下各条路的权重和，找到最小的。-I hope that in secshortest only a short time, the result is out of several, so when used to get at short circuit, can only be used roadcost () function, respectively,