I just got AC for this dynamic programming problem 401D - Roman and Numbers after many trials using recursion then loops..

I have faced some behaviour, which -in my opinion- is strange, and I can't figure out why it behaves like that :

1. Declaring the dp array like this : dp[100][1<<18] gives a TLE. However, dp[1<<18][100] doesn't.
2. using a long long for bitmask is slower than int! I know that 32bit integer would be sufficient for this problem, but I thought it would be safer to use long long.

I hope someone can explain it for me, thanks a lot :D