//一个解数独的程序，纯C编写，不依赖特殊库，移植容易。个人原创！

//采用的回溯法，剪枝程序采用动态规划思想进行了大量优化，比一般数独程序可以统计用多少步，中间碰到多少分支，侧面反映题目难度，虽然不能和人的技巧相比，也可以参考一下。

//对于研究数独方法或许没有帮助，但是可以帮助验证结果，统计难度。对于出题时可以去掉的项，也可用其验证。有代码，看懂后可以随便修改。

//解世界上最难数独大概1s左右

//程序作者：原建业-Sudoku @ a program written in pure C, do not rely on special libraries, easy to transplant. Personal originality!

@ Uses backtracking, pruning program uses dynamic programming to optimize a lot, than the average Sudoku program can count the number of steps used, the number of branches across the middle, the reflection of the difficulty of the subject, although it is not and people skills compared You can also refer to.

@ Sudoku method for the study may not help, but it can help verify the results, statistics difficult. For questions can be removed when the entry is also available in its validation. There code, you can easily modify the read.

@ Solution is probably the most difficult sudoku 1s around the world