说明：  概率算法的一个基本特征是对所求解问题的同一实例用同一概率算法求解两次可能得到完全不同的效果。这两次求解问题所需的时间甚至所得到的结果可能会有相当大的差别。
(probability of a basic algorithm is characterized by solving problems on the same case with the same probability algorithm may be two be completely different results. Solving these two problems required even by the time the results may be quite different.)