static boolean isKAlternating ( String s , int k ) {
  if ( s . length ( ) < k ) return false ;
  int checker = 0 ;
  for ( int i = 0 ;
  i < k ;
  i ++ ) {
    int bitAtIndex = s . charAt ( i ) - 'a' ;
    if ( ( checker & ( 1 << bitAtIndex ) ) > 0 ) {
      return false ;
    }
    checker = checker | ( 1 << bitAtIndex ) ;
  }
  for ( int i = k ;
  i < s . length ( ) ;
  i ++ ) if ( s . charAt ( i - k ) != s . charAt ( i ) ) return false ;
  return true ;
}

static boolean isKAlternating ( String s , int k ) { if ( s . length ( ) < k ) return false ; int checker = 0 ; for ( int i = 0 ; i < k ; i ++ ) { int bitAtIndex = s . charAt ( i ) - ' a ' ; if ( ( checker & ( 1 << bitAtIndex ) ) > 0 ) { return false ; } checker = checker | ( 1 << bitAtIndex ) ; } for ( int i = k ; i < s . length ( ) ; i ++ ) if ( s . charAt ( i - k ) != s . charAt ( i ) ) return false ; return true ; }
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