用递归写伪币问题。n块相同的金币中有且仅有一块假币．该假币一定比真正的金币轻，要求用一没有砝码的天平，用尽量少的称量次数找出假币，模拟该过程-Recursively write the counterfeit coins problem. n blocks of gold and only a counterfeit money. The counterfeit money must be lighter than real gold, the requirements to identify counterfeit money, not weight the scales, weighing less exhausted, to simulate the process of it.