1.Use a DP with the O(30N) time
2.Use ternary (long long in C++ is needed) to indicate each solution
3.Use a rolling array in case it MLEs

Good luck! ~_~

Edited by author 05.07.2011 19:05

Meet-in-the-middle is easier, I think. I have solved using both methods, it's faster and shorter.

no need for longlong