问Trie实现问题

EN

class State  // could be struct or whatever
{
    int valid; // can handle 32 transitions -- each bit set is valid
    vector<State> transitions;

    State getNextState( int ch )
    {
         int index;
         int mask  = ( 1 << ( toupper( ch ) - 'A' )) -1;
         int bitsToCount = valid & mask;

         for( index = 0; bitsToCount ; bitsToCount  >>= 1)
         {
             index  += bitsToCount  & 1;
         }  
         transitions.at( index );
    }
};

class State
{
    State transitions[ 26 ]; // use the char as the index.

    State getNextState( int ch )
    {
        return transitions[ ch ];
    }
};