https://leetcode.com/problems/integer-to-roman/
原题：
Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.
思路：
掌握罗马数字规则并实现即可。（具体规则见 LeetCode(13)：Roman to Integer）
我的AC代码：
1 class Solution { 2 public: 3 string intToRoman(int num) { 4 string in[] = {"I","V","X","L","C","D","M"}; 5 int t,i=0,j=0; 6 string res="",tmp=""; 7 // cout<<(tmp += in[0]+in[1]); 8 while(num>0){ 9 t=num%10; 10 switch (t){ 11 case 0: break; 12 case 1: tmp = in[i]; break; 13 case 2: tmp = in[i]+in[i]; break; 14 case 3: tmp = in[i]+in[i]+in[i]; break; 15 case 4: tmp = in[i]+in[i+1]; break; 16 case 5: tmp = in[i+1]; break; 17 case 6: tmp = in[i+1]+in[i]; break; 18 case 7: tmp = in[i+1]+in[i]+in[i]; break; 19 case 8: tmp = in[i+1]+in[i]+in[i]+in[i]; break; 20 case 9: tmp = in[i]+in[i+2]; break; 21 } 22 i += 2; 23 // cout<<in[1]+in[0]+in[0]+in[0]<<" "<<tmp<<endl; 24 res = tmp +res; 25 num=num/10; 26 tmp=""; 27 } 28 cout<< res; 29 return res; 30 } 31 };