Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.
Symbol & Value
I
= 1
V
= 5
X
= 10
L
= 50
C
= 100
D
= 500
M
= 1000
For example, 2
is written as II
in Roman numeral, just two ones added together. 12
is written as XII
, which is simply X + II
. The number 27
is written as XXVII
, which is XX + V + II
.
Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII
. Instead, the number four is written as IV
. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX
. There are six instances where subtraction is used:
-
I
can be placed beforeV
(5) andX
(10) to make 4 and 9. -
X
can be placed beforeL
(50) andC
(100) to make 40 and 90. -
C
can be placed beforeD
(500) andM
(1000) to make 400 and 900.
Given a roman numeral, convert it to an integer.
Input: romanNumber = "III"
Output: 3
Explanation: III = 3
Input: romanNumber = "LVIII"
Output: 358
Explanation: L = 50, V= 5, III = 3
Input: romanNumber = "MCMXCIV"
Output: 1994
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.