Very improved combine algorithm and added a method to obtain the k-esima solution without calculating all of them.
Very improved combine algorithm and added a method to obtain the k-esima solution without calculating all of them.

sohonetlabs/qbe,laiyonghao/qbe,versae/qbe,laiyonghao/qbe,laiyonghao/qbe,versae/qbe,sohonetlabs/qbe,sohonetlabs/qbe,versae/qbe