Integer to Roman

来源：Leetcode

原帖：http://oj.leetcode.com/problems/integer-to-roman/

题目：
Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. Solution: Buffer the roman numbers. Conversion range from high bit to low bit.

代码：
1]

 class Solution {  
 public:  
   const string rom[4][10] = {{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"},  
                 {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"},  
                 {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"},  
                 {"", "M", "MM", "MMM"}};  
   
   string intToRoman(int num) {  
     string res;  
     int i = 3;  
     while (num > 0) {  
       int divisor = (int)pow(10, i);  
       res += rom[i][num / divisor];  
       num %= divisor;  
       i--;  
     }  
     return res;  
   }  
 };  

2]

 class Solution {  
 public:  
   string intToRoman(int num) {  
     vector<int> value = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};  
     unordered_map<int, string> map = {{1000, "M"}, {900, "CM"}, {500, "D"}, {400, "CD"},  
                     {100, "C"}, {90, "XC"}, {50, "L"}, {40, "XL"}, {10, "X"},  
                     {9, "IX"}, {5, "V"}, {4, "IV"}, {1, "I"}};  
     int i=0;  
     string res;  
     while (num) {  
       if (num >= value[i]) {  
         num -= value[i];  
         res += map[value[i]];  
       } else {  
         i++;  
       }  
     }  
     return res;  
   }  
 };