y not try it out here on codeforces ? 16E - Fish

Without having a closer look on the problem and just looking at the code, these are the optimizations I can suggest.

• Optimize I/O, e.g. use PrintWriter for output. In this case you don't output a massive amount of numbers, so this should only make a small difference (but maybe a necessary one?).
• Move out the if((mask&1<<i)!=0) part of the if-statement in the DP a loop level.
• Divisions are expensive so move out the /pairs part from both loops in the DP, i.e. change to dp[mask] /= pairs.
• I guess some time is spent in the BitCount function, especially considering it contains a modulo operation, eliminate the need and use of this function by simply keeping track of the number of ones as you move along.

Main optimization for getting AC on SPOJ — change recursion with memoization to calculating dp with for-loop.

And it need to move out clause if((mask&(1 << i)) != 0) on "i" loop level, as Klein mentioned.

This code got AC on SPOJ: link to Ideone

Thank you so much Klein and Slamur .