public/subjects/romannumbers

romannumbers

Instructions

Write a program called rn. The objective is to convert a number, given as an argument, into a roman number and print it with its roman number calculation.

The program should have a limit of 4000. In case of an invalid number, for example "hello" or 0 the program should print ERROR: cannot convert to roman digit.

Roman Numerals reminder:

I	1
V	5
X	10
L	50
C	100
D	500
M	1000

For example, the number 1732 would be denoted MDCCXXXII in Roman numerals. However, Roman numerals are not a purely additive number system. In particular, instead of using four symbols to represent a 4, 40, 9, 90, etc. (i.e., IIII, XXXX, VIIII, LXXXX, etc.), such numbers are instead denoted by preceding the symbol for 5, 50, 10, 100, etc., with a symbol indicating subtraction. For example, 4 is denoted IV, 9 as IX, 40 as XL, etc.

The following table gives the Roman numerals for the first few positive integers.

1	I	11	XI	21	XXI
2	II	12	XII	22	XXII
3	III	13	XIII	23	XXIII
4	IV	14	XIV	24	XXIV
5	V	15	XV	25	XXV
6	VI	16	XVI	26	XXVI
7	VII	17	XVII	27	XXVII
8	VIII	18	XVIII	28	XXVIII
9	IX	19	XIX	29	XXIX
10	X	20	XX	30	XXX

Usage

$ go run . hello
ERROR: cannot convert to roman digit
$ go run . 123
C+X+X+I+I+I
CXXIII
$ go run . 999
(M-C)+(C-X)+(X-I)
CMXCIX
$ go run . 3999
M+M+M+(M-C)+(C-X)+(X-I)
MMMCMXCIX
$ go run . 4000
ERROR: cannot convert to roman digit
$