unique array without using unique

Write a System Verilog code with a array (say with 20 elements) where all the array elements have unique numbers. The numbers can be any integer value.
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Answer:

module unique_array_element;
class array_ele;
  rand bit [7:0] data[];
  constraint data_values { foreach(data[i]) 
                             foreach(data[j])
                               if(i != j) data[i] != data [j] ;} 
endclass

  array_ele array_ele_obj;

  initial
  begin
     array_ele_obj = new();
     array_ele_obj.data = new[20];
     assert(randomize(array_ele_obj));
     foreach(array_ele_obj.data[i])
      $display("%d",array_ele_obj.data[i]);
  end
endmodule