题目：
Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.
思路：
主要是了解罗马数和阿拉伯数字的对应关系，如下表：
由这个表基本上可以将1-3999范围的阿拉伯数字换成罗马数字。在处理阿拉伯数字时从高位开始匹配，将每个位的值找出对应罗马数字，串成字符串即可。
public class Solution {
public String intToRoman(int num) {
int[] val={1000,900,500,400,100,90,50,40,10,9,5,4,1};
String[] sym={"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
String rom="";
for(int i=0;i<val.length;i++){
while(num>=val[i]){
rom+=sym[i];
num-=val[i];
}
}
return rom;
}
}