search through all the indiced at which the current character occurs . For each index greater than prev , take the index and move to the next position , and add to the answer .
answer = 0 NEW_LINE for i in range ( len ( index ) ) : NEW_LINE INDENT if ( index [ i ] > prev ) : NEW_LINE INDENT answer = ( answer % mod + calculate ( pos + 1 , index [ i ] , s , index ) % mod ) % mod NEW_LINE DEDENT DEDENT dp [ pos ] [ prev ] = 4 NEW_LINE