0012. Integer to Roman

# 12. Integer to Roman#

## 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 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`

## 题目大意 #

• 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。

## 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 #

``````package leetcode

func intToRoman(num int) string {
values := []int{1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1}
symbols := []string{"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"}
res, i := "", 0
for num != 0 {
for values[i] > num {
i++
}
num -= values[i]
res += symbols[i]
}
return res
}
`````` Sep 18, 2021 Edit this page