51. Opcode Decoder

module alu_decoder (
    input  [1:0] opcode,
    output reg [3:0] alu_op
);
    always @* begin
        case (opcode)
            // Write solution here
            2'b00:   alu_op = 4'b0001;
            2'b01:   alu_op = 4'b0010;
            2'b10:   alu_op = 4'b0100;
            2'b11:   alu_op = 4'b1000;
            default: alu_op = 4'b0000;
        endcase
    end
endmodule