在许多情况下我们需要穷举组合的算法，比如密码词典。这个算法的关键是密码下标进位的问题。另外本例子中的写文件语句效率比较低，为了降低算法复杂度没有优化。如果要提高写文件的效率，可以使用缓冲区，分批写入。-in many cases we need exhaustive combination of algorithms such as password dictionary. The algorithm is the key indices into password-issue. Another example of this document written statement low efficiency, in order to reduce the complexity of the algorithm has not been optimized. If the document was to improve the efficiency, the use of buffer zones, into batches.