Stores digits present in string v [ i ] atleast once . We use a set as we only need digits which exist only once ( irrespective of reputation )
let digits = new Set ( ) ; for ( let j = 0 ; j < v [ i ] . length ; j ++ ) digits . add ( ( v [ i ] [ j ] ) . charCodeAt ( 0 ) - ' ' . charCodeAt ( 0 ) ) ;