public static void main ( String [ ] args ) {
  Scanner scanner = new Scanner ( System . in ) ;
  int q = scanner . nextInt ( ) ;
  for ( int i = 0 ;
  i < q ;
  i ++ ) {
    int n = scanner . nextInt ( ) ;
    int a [ ] = new int [ n ] ;
    for ( int j = 0 ;
    j < n ;
    j ++ ) {
      a [ j ] = scanner . nextInt ( ) ;
    }
    Arrays . sort ( a ) ;
    boolean flag = false ;
    for ( int j = 1 ;
    j < n ;
    j ++ ) {
      if ( Math . abs ( a [ j - 1 ] - a [ j ] ) == 1 ) {
        flag = true ;
        break ;
      }
      else {
        flag = false ;
      }
    }
    System . out . println ( flag ? 2 : 1 ) ;
  }
}

public static void main ( String [ ] args ) { Scanner scanner = new Scanner ( System . in ) ; int q = scanner . nextInt ( ) ; for ( int i = 0 ; i < q ; i ++ ) { int n = scanner . nextInt ( ) ; int a [ ] = new int [ n ] ; for ( int j = 0 ; j < n ; j ++ ) { a [ j ] = scanner . nextInt ( ) ; } Arrays . sort ( a ) ; boolean flag = false ; for ( int j = 1 ; j < n ; j ++ ) { if ( Math . abs ( a [ j - 1 ] - a [ j ] ) == 1 ) { flag = true ; break ; } else { flag = false ; } } System . out . println ( flag ? 2 : 1 ) ; } }
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