Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

[解题思路]

这道题主要就在于如何处理每一位digit，并且按照区间不同处理：

1<=digit <=3

digit =4

digit = 5

5<digit<=8

digit =9

[Code]

1:  string intToRoman(int num) {  2:      // Start typing your C/C++ solution below  3:      // DO NOT write int main() function    4:      char symbol[7] = { 'I','V','X', 'L','C', 'D','M'};  5:      string roman;  6:      int scale = 1000;  7:      for(int i =6; i>=0; i-=2)  8:      {  9:        int digit = num/scale;  10:        if(digit != 0)  11:        {        12:          if(digit <= 3)  13:          {  14:            roman.append(digit, symbol[i]);  15:          }  16:          else if(digit ==4)  17:          {  18:            roman.append(1, symbol[i]);  19:            roman.append(1, symbol[i+1]);  20:          }  21:          else if(digit ==5)  22:          {  23:            roman.append(1, symbol[i+1]);  24:          }  25:          else if(digit <=8)  26:          {  27:            roman.append(1, symbol[i+1]);  28:            roman.append(digit-5, symbol[i]);  29:          }  30:          else if(digit ==9)  31:          {  32:            roman.append(1, symbol[i]);  33:            roman.append(1, symbol[i+2]);  34:          }  35:        }  36:        num = num%scale;  37:        scale/=10;        38:      }  39:      return roman;  40:    }