12. Integer to Roman

Description

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 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. Input is guaranteed to be within the range from 1 to 3999.

Example 1:

Input: 3
Output: "III"

Example 2:

Input: 4
Output: "IV"

Example 3:

Input: 9
Output: "IX"

Example 4:

Input: 58
Output: "LVIII"
Explanation: C = 100, L = 50, XXX = 30 and III = 3.

Example 5:

Input: 1994
Output: "MCMXCIV"
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

Tags: Math, String

题意

整型数转罗马数字,范围从 1 到 3999

题解

思路1

查看下百度百科的罗马数字介绍如下:

  • 相同的数字连写,所表示的数等于这些数字相加得到的数,如 Ⅲ=3;

  • 小的数字在大的数字的右边,所表示的数等于这些数字相加得到的数,如 Ⅷ=8、Ⅻ=12;

  • 小的数字(限于 Ⅰ、X 和 C)在大的数字的左边,所表示的数等于大数减小数得到的数,如 Ⅳ=4、Ⅸ=9。

那么我们可以把整数的每一位分离出来,让其每一位都用相应的罗马数字位表示,最终拼接完成。比如 621 我们可以分离百、十、个分别为 621,那么 600 对应的罗马数字是 DC20 对应的罗马数字是 XX1 对应的罗马数字是 I,所以最终答案便是 DCXXI

func intToRoman(num int) string {
    i := [10]string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}
    x := [10]string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}
    c := [10]string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}
    m := [4]string{"", "M", "MM", "MMM"}
    return m[num/1000] + c[num%1000/100] + x[num%1000%100/10] + i[num%1000%100%10]
}

思路2

思路2 ```go

```

结语

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