[leetcode] 12. Integer to Roman numeral

12、 Integer to Roman number

subject ：

Roman numerals contain the following seven characters ： I, V, X, L,C,D and M.

 character            The number 
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

for example , Rome digital 2 Write to do II , Two parallel 1.12 Write to do XII , That is to say X + II . 27 Write to do XXVII, That is to say XX + V + II .

Usually , The small numbers in roman numbers are to the right of the big ones . But there are special cases , for example 4 Do not write IIII, It is IV. Numbers 1 In number 5 Left side , The number represented is equal to the large number 5 Decimal reduction 1 Value obtained 4 . similarly , Numbers 9 Expressed as IX. This special rule only applies to the following six cases ：

I Can be placed in V (5) and X (10) Left side , To express 4 and 9.
X Can be placed in L (50) and C (100) Left side , To express 40 and 90.
C Can be placed in D (500) and M (1000) Left side , To express 400 and 900.
Give you an integer , Turn it into Roman numerals .

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"
 explain : L = 50, V = 5, III = 3.

Example 5:

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

Their thinking ：

Ideas for solving this problem , More , For example, greedy algorithm , Violence , enumeration . Splicing and so on .
Let's use the splicing method to realize ：

Reference code ：

class Solution {
    
    public String intToRoman(int num) {
    
        int[] values={
    1000,900,500,400,100,90,50,40,10,9,5,4,1};
        String[] rom={
    "M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};

        StringBuilder sb=new StringBuilder();
        
        for(int i=0;i<values.length;i++){
    
            while(num>=values[i]){
    
                sb.append(rom[i]);
                num-=values[i];
            }
        }

        return sb.toString();
    }
}