12. 整数转罗马数字
12. 整数转罗马数字
题目
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 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 an integer, convert it to a roman numeral.
Example 1:
Input: num = 3
Output: "III"
Explanation: 3 is represented as 3 ones.
Example 2:
Input: num = 58
Output: "LVIII"
Explanation: L = 50, V = 5, III = 3.
Example 3:
Input: num = 1994
Output: "MCMXCIV"
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
Constraints:
1 <= num <= 3999
题目大意
通常情况下,罗马数字中小的数字在大的数字的右边。但也存在特例,例如 4
不写做 IIII
,而是 IV
。数字 1
在数字 5
的左边,所表示的数等于大数 5
减小数 1
得到的数值 4
。同样地,数字 9
表示为 IX
。这个特殊的规则只适用于以下六种情况:
I
可以放在V (5)
和X (10)
的左边,来表示4
和9
。X
可以放在L (50)
和C (100)
的左边,来表示40
和90
。C
可以放在D (500)
和M (1000)
的左边,来表示400
和900
。
给定一个整数,将其转为罗马数字。输入确保在 1
到 3999
的范围内。
解题思路
- 依照题意,优先选择大的数字,解题思路采用贪心算法。将
1-3999
范围内的罗马数字从大到小放在数组中,从头选择到尾,即可把整数转成罗马数字。
代码
/**
* @param {number} num
* @return {string}
*/
var intToRoman = function (num) {
const int = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
const roman = [
'M',
'CM',
'D',
'CD',
'C',
'XC',
'L',
'XL',
'X',
'IX',
'V',
'IV',
'I'
];
let res = '';
for (let i = 0; i < int.length; i++) {
while (num >= int[i]) {
res += roman[i];
num -= int[i];
}
}
return res;
};
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