政子的博客

技术|学习|随笔

LeetCode-Integer to Roman

https://leetcode-cn.com/problems/integer-to-roman/

大概就是直接翻译题意，一遍通过。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
class Solution {
    public String intToRoman(int num) {
        char[] convertArr={'I','V','X','L','C','D','M'};
        int currentPos=0;
        StringBuilder sb=new StringBuilder();
        while(num>0){
            int t=num%10;
            num/=10;
            if(t<5){
                if(t==4){
                    sb.append(convertArr[currentPos+1]);
                    sb.append(convertArr[currentPos]);
                }else{
                    for(int i=0;i<t;i++) sb.append(convertArr[currentPos]);
                }
            }else{
                if(t==9){
                    sb.append(convertArr[currentPos+2]);
                    sb.append(convertArr[currentPos]);
                }else{
                    for(int i=0;i<t-5;i++) sb.append(convertArr[currentPos]);
                    sb.append(convertArr[currentPos+1]);
                }
            }
            currentPos+=2;
        }
        return sb.reverse().toString();
    }
}

看了答案以后发现了更方便的解法，直接穷举特殊 case，然后去减。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
class Solution {
    public String intToRoman(int num) {
        String[] romans=new String[] {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
        int[] nums=new int[] {1000,900,500,400,100,90,50,40,10,9,5,4,1};
        StringBuilder sb=new StringBuilder();
        for(int i=0;i<nums.length;i++){
            while(nums[i]<=num){
                sb.append(romans[i]);
                num-=nums[i];
            }
        }
        return sb.toString();
    }
}