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 to exhaustive combinations of algorithms, such as the password dictionary.// This algorithm, the key is password subscr ipt binary problems.// Another example of this statement to write a document relatively low efficiency, in order to reduce the algorithm complexity is not optimized. If you want to improve the efficiency of writing documents, you can use the buffer, write in batches.