IntegertoRoman.cs

// Source : https://leetcode.com/problems/integer-to-roman/ 
// Author : codeyu 
// Date : 10/4/16 

/***************************************************************************************
*
* Given an integer, convert it to a roman numeral.
* 
* Input is guaranteed to be within the range from 1 to 3999.
*
**********************************************************************************/

using System;
using System.Collections.Generic;
using System.Text;
namespace Algorithms
{
    public class Solution012 
    {
        public static string IntToRoman(int num) 
        {
            if(num < 0 || num > 3999)
            {
                return "";
            }
            string str = "";    
            string [] symbol = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};    
            int [] value = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};   
            for(int i=0;num!=0;i++)
            {  
                while(num >= value[i])
                {  
                    num -= value[i];  
                    str += symbol[i];  
                }  
            }  
            return str;  
            
        }
        public static string IntToRoman2(int num) 
        {
            char[] symbol = {'I','V','X','L','C','D','M'};
            StringBuilder roman = new StringBuilder();
            int scale = 1000;
            int p = 6;
            while(num > 0)
            {
                int digit = num / scale;
                if(digit > 0 && digit < 10)
                {
                    roman.Append(RomanStr(digit, symbol, p));
                }
			    num = num % scale;
			    scale /= 10;
			    p -= 2;
            }
            return roman.ToString();
        }
        private static string RomanStr(int digit, char[] symbol, int p)
        {
            StringBuilder roman = new StringBuilder();
            if(digit <= 3) roman.Append(symbol[p], digit);
            else if(digit == 4){
                roman.Append(symbol[p]);
                roman.Append(symbol[p+1]);
            }else if(digit <= 8){
                roman.Append(symbol[p+1]);
                roman.Append(symbol[p], digit-5);
            }else if(digit == 9){
                roman.Append(symbol[p]);
                roman.Append(symbol[p+2]);
            }
            return roman.ToString();
        }
    }
}