public static void main ( String args [ ] ) {
  Scanner s = new Scanner ( System . in ) ;
  int t = s . nextInt ( ) ;
  while ( t -- != 0 ) {
    int n = s . nextInt ( ) ;
    int arr [ ] = new int [ 2 * n ] ;
    for ( int i = 0 ;
    i < 2 * n ;
    i ++ ) {
      arr [ i ] = s . nextInt ( ) ;
    }
    Arrays . sort ( arr ) ;
    System . out . println ( arr [ n ] - arr [ n - 1 ] ) ;
  }
}

public static void main ( String args [ ] ) { Scanner s = new Scanner ( System . in ) ; int t = s . nextInt ( ) ; while ( t -- != 0 ) { int n = s . nextInt ( ) ; int arr [ ] = new int [ 2 * n ] ; for ( int i = 0 ; i < 2 * n ; i ++ ) { arr [ i ] = s . nextInt ( ) ; } Arrays . sort ( arr ) ; System . out . println ( arr [ n ] - arr [ n - 1 ] ) ; } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (type_identifier) name: (identifier) dimensions: (dimensions))) 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)))) (while_statement condition: (parenthesized_expression (binary_expression left: (update_expression (identifier)) right: (decimal_integer_literal))) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) dimensions: (dimensions) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (binary_expression left: (decimal_integer_literal) right: (identifier)))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (binary_expression left: (decimal_integer_literal) right: (identifier))) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (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: (array_access array: (identifier) index: (identifier)) right: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal)))))))))))