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 one's 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 before V
(5) and X
(10) to make 4 and 9. X
can be placed before L
(50) and C
(100) to make 40 and 90. C
can be placed before D
(500) and M
(1000) to make 400 and 900.Given an integer, convert it to a roman numeral.
Example 1:
Input: num = 3 Output: "III"
Example 2:
Input: num = 4 Output: "IV"
Example 3:
Input: num = 9 Output: "IX"
Example 4:
Input: num = 58 Output: "LVIII" Explanation: L = 50, V = 5, III = 3.
Example 5:
Input: num = 1994 Output: "MCMXCIV" Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
Constraints:
1 <= num <= 3999
struct Solution;
impl Solution {
fn int_to_roman(mut num: i32) -> String {
let mapping: Vec<(i32, &str)> = vec![
(1, "I"),
(2, "II"),
(3, "III"),
(4, "IV"),
(5, "V"),
(6, "VI"),
(7, "VII"),
(8, "VIII"),
(9, "IX"),
(10, "X"),
(20, "XX"),
(30, "XXX"),
(40, "XL"),
(50, "L"),
(60, "LX"),
(70, "LXX"),
(80, "LXXX"),
(90, "XC"),
(100, "C"),
(200, "CC"),
(300, "CCC"),
(400, "CD"),
(500, "D"),
(600, "DC"),
(700, "DCC"),
(800, "DCCC"),
(900, "CM"),
(1000, "M"),
(2000, "MM"),
(3000, "MMM"),
];
let mut res: String = "".to_string();
for (x, s) in mapping.iter().rev() {
if num >= *x {
res += s;
num -= x;
} else {
continue;
}
if num == 0 {
break;
}
}
res
}
}
#[test]
fn test() {
let num = 3;
let res = "III".to_string();
assert_eq!(Solution::int_to_roman(num), res);
let num = 1994;
let res = "MCMXCIV".to_string();
assert_eq!(Solution::int_to_roman(num), res);
}