Write a perfect hash function to hash 5 by 5 tic tac toe boards, i.e. 5 by 5 arrays of char where each element has one of three values ('X', 'O' or '_').

Perfect means no two distinct boards hash to the same value, provided a big enough hash table size. To avoid integer overflow, you can use long long int rather than int as the return type and the size parameter type.

Your function will have prototype long long int hashBoard(char[][5], long long int size).