51. Opcode Decoder

How do you plan to solve it?

module alu_decoder (
    input  [1:0] opcode,
    output reg [3:0] alu_op
);
    always @* begin
        case (opcode)
            2'b00: alu_op = 1;
            2'b01: alu_op = 2;
            2'b10: alu_op = 4;
            2'b11: alu_op = 8;
            default: alu_op = 0;
        endcase
    end
endmodule