回溯（b a c k t r a c k i n g）是一种系统地搜索问题解答的方法。为了实现回溯，首先需要为问题定义一个解空间（ solution space），这个空间必须至少包含问题的一个解（可能是最优的）。在迷宫老鼠问题中，我们可以定义一个包含从入口到出口的所有路径的解空间；在具有n 个对象的0 / 1背包问题中（见1 . 4节和2 . 2节），解空间的一个合理选择是2n 个长度为n 的0 / 1向量的集合，这个集合表示了将0或1分配给x的所有可能方法。当n= 3时，解空间为{ ( 0 , 0 , 0 )，( 0 , 1 , 0 )，( 0 , 0 , 1 )，( 1 , 0 , 0 )，( 0 , 1 , 1 )，( 1 , 0 , 1 )，( 1 , 1 , 0 )，( 1 , 1 , 1 ) }。-retrospective (b a c k t r a c k i n g) is a systematic search to answer the question. To achieve retrospective, the first issue of the need for a definition of the solution space (solution space), The space must contain at least one solution to the problem (which may be optimal). Rats in a maze problem, we can contain a definition from the entrance to the export of the solution space trails; n is the object of the 0 / 1 knapsack problem (see 1. 4 and 2. 2) The solution space is a reasonable choice of two n length of the 0 n / a vector set, this assembly that it will 0 or 1 x allocated to all possible ways. When n = 3, the solution space for the ((0, 0, 0), (0, 1, 0), (0, 0, 1), (1, 0, 0), (0, 1, 1), (1, 0, 1), (1, 1, 0), (1, 1, 1)).