public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int tc = sc . nextInt ( ) ;
  for ( ;
  tc > 0 ;
  tc -- ) {
    int n = sc . nextInt ( ) ;
    n = n * 2 ;
    ArrayList < Integer > a = new ArrayList < Integer > ( ) ;
    for ( int i = 0 ;
    i < n ;
    ++ i ) {
      a . add ( sc . nextInt ( ) ) ;
    }
    Collections . sort ( a ) ;
    System . out . println ( a . get ( n / 2 ) - a . get ( n / 2 - 1 ) ) ;
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int tc = sc . nextInt ( ) ; for ( ; tc > 0 ; tc -- ) { int n = sc . nextInt ( ) ; n = n * 2 ; ArrayList < Integer > a = new ArrayList < Integer > ( ) ; for ( int i = 0 ; i < n ; ++ i ) { a . add ( sc . nextInt ( ) ) ; } Collections . sort ( a ) ; System . out . println ( a . get ( n / 2 ) - a . get ( n / 2 - 1 ) ) ; } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (for_statement condition: (binary_expression left: (identifier) right: (decimal_integer_literal)) update: (update_expression (identifier)) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) (local_variable_declaration type: (generic_type (type_identifier) (type_arguments (type_identifier))) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (generic_type (type_identifier) (type_arguments (type_identifier))) arguments: (argument_list)))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (decimal_integer_literal)))) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal))))))))))))