13. 罗马数字转整数
13. 罗马数字转整数
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, two is written as II
in Roman numeral, just two one's added together. Twelve is written as, XII
, which is simply X
+ II
. The number twenty seven 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.
Example 1:
Input: s = "III"
Output: 3
Explanation: III = 3.
Example 2:
Input: s = "LVIII"
Output: 58
Explanation: L = 50, V= 5, III = 3.
Example 3:
Input: s = "MCMXCIV"
Output: 1994
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
Constraints:
1 <= s.length <= 15
s
contains only the characters('I', 'V', 'X', 'L', 'C', 'D', 'M')
.- It is guaranteed that
s
is a valid roman numeral in the range[1, 3999]
.
题目大意
罗马数字包含以下七种字符: I, V, X, L, C, D, M
。
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:
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
。
给定一个罗马数字,将其转换成整数。输入确保在 1
到 3999
的范围内。
解题思路
按照题目中罗马数字的字符数值,计算出对应罗马数字的十进制数即可。
代码
/**
* @param {string} s
* @return {number}
*/
var romanToInt = function (s) {
const roman = {
I: 1,
V: 5,
X: 10,
L: 50,
C: 100,
D: 500,
M: 1000
};
let num, nextNum;
let total = 0;
for (let i = 0; i < s.length; i++) {
num = roman[s[i]];
nextNum = roman[s[i + 1]];
if (num < nextNum) {
total -= num;
} else {
total += num;
}
}
return total;
};
相关题目
题号 | 标题 | 题解 | 标签 | 难度 | 力扣 |
---|---|---|---|---|---|
12 | 整数转罗马数字 | [✓] | 哈希表 数学 字符串 | 🟠 | 🀄️ 🔗 |