Leetcode -- 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.

分析：罗马数字，转到阿拉伯数字是相当有规律的。比如9 -- IX， 90 -- XC， 99  -- XCIX

思路：map形式，将所有特殊的都存储起来，然后在直接通过key获取相应的值。

代码：

string intToRoman(int num) {        map <int, map<int, string>>map1;          map1[10][1] = "I";        map1[10][2] = "II";        map1[10][3] = "III";        map1[10][4] = "IV";        map1[10][5] = "V";        map1[10][6] = "VI";        map1[10][7] = "VII";        map1[10][8] = "VIII";        map1[10][9] = "IX";                map1[100][1] = "X";        map1[100][2] = "XX";        map1[100][3] = "XXX";        map1[100][4] = "XL";        map1[100][5] = "L";        map1[100][6] = "LX";        map1[100][7] = "LXX";        map1[100][8] = "LXXX";        map1[100][9] = "XC";                map1[1000][1] = "C";        map1[1000][2] = "CC";        map1[1000][3] = "CCC";        map1[1000][4] = "CD";        map1[1000][5] = "D";        map1[1000][6] = "DC";        map1[1000][7] = "DCC";        map1[1000][8] = "DCCC";        map1[1000][9] = "CM";                map1[10000][1] ="M";        map1[10000][2] = "MM";        map1[10000][3] = "MMM";                int a = 10;        int b;        string s = "";        while(num)        {            b = num%10;            if(b != 0)            {                s = map1[a][b] + s;            }            num = num/10;            a = a * 10;        }        return s;    }

更为简单的解法（网上抄的-_-）：

1.  public String intToRoman(int number) {  
2.         int[] values = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 };  
3.         String[] numerals = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };  
4.         StringBuilder result = new StringBuilder();  
5.         for (int i = 0; i < values.length; i++) {  
6.             while (number >= values[i]) {  
7.                 number -= values[i];  
8.                 result.append(numerals[i]);  
9.             }  
10.         }  
11.         return result.toString();  
12.     }