leetCode/src/main/java/com/leetcode/huawei/IntToRoman.java

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package com.leetcode.huawei;
/**
*
* 整数转罗马数字
*罗马数字包含以下七种字符 I V X LCD  M。
字符 数值
I 1
V 5
X 10
L 50
C 100
D 500
M 1000
例如, 罗马数字 2 写做 II 即为两个并列的 1。12 写做 XII 即为 X + II 。 27 写做  XXVII, 即为 XX + V + II 
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。
示例 1:
输入: 3
输出: "III"
示例 2:
输入: 4
输出: "IV"
示例 3:
输入: 9
输出: "IX"
示例 4:
输入: 58
输出: "LVIII"
解释: L = 50, V = 5, III = 3.
示例 5:
输入: 1994
输出: "MCMXCIV"
解释: M = 1000, CM = 900, XC = 90, IV = 4.
 
提示:
1 <= num <= 3999
来源力扣LeetCode
链接https://leetcode-cn.com/problems/integer-to-roman
著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。
*/
public class IntToRoman {
int[] keys = {1000, 900, 500, 400, 100,90, 50, 40, 10, 9, 5, 4, 1};
String[] values = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X","IX", "V", "IV", "I"};
public String intToRoman(int num) {
StringBuffer buffer = new StringBuffer();
for (int i = 0; i < keys.length; i++) {
while (num >= keys[i]) {
buffer.append(values[i]);
num -= keys[i];
}
}
return buffer.toString();
}
public static void main(String[] args) {
IntToRoman toRoman = new IntToRoman();
int num = 1994;
String res = toRoman.intToRoman(num);
System.out.println(res);
}
}