text: map is used to store character frequencies
code: Map < Character , Integer > mp = new HashMap < > ( ) ; for ( i = 0 ; i < s . length ; i ++ ) { mp . put ( s [ i ] , mp . get ( s [ i ] ) == null ? 1 : mp . get ( s [ i ] ) + 1 ) ; } int sum = 0 , product = 1 ;