count number of unique alphabets in each string
for ( int k = 0 ; k < na [ j ] . length ( ) ; k ++ ) { int x = na [ j ] . charAt ( k ) - ' A ' ; if ( ( na [ j ] . charAt ( k ) != ' ▁ ' ) && ( character [ x ] == false ) ) { c [ j ] ++ ; character [ x ] = true ; } }