leetcode 12 Integer to Roman

题目详情

Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.

题目的意思是： 输入一个阿拉伯数字，我们需要输出这个数字的罗马数字表示形式（字符串）。

想法

• 这道题最重要的点就是理解罗马数和阿拉伯数之间的转换规律。
• 1000[M],500[D],100[C],50[L],10[X],5[V],1[I]这是基本转换
• 但是还有一些特殊情况900[CM]：这种情况就是左边的这个罗马字符代表的数、减去右边的这个罗马字符代表的数才得到900。相似的有400[CD],90[XC],40[XL],9[IX],4[IV]

解法

    public String intToRoman(int num) {
        
        if(num < 1)return "";
        int[] numbers = {1000,900,500,400,100,90,50,40,10,9,5,4,1};
        String[] roman = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
        StringBuilder res = new StringBuilder();
        
        for(int i=0;i<numbers.length;i++){
            while(num >= numbers[i]){
                num -= numbers[i];
                res.append(roman[i]);
            }
        }
        
        
        return res.toString();
    }