12：Integer to Roman（数字转为罗马数字）

问题描述
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
题目的要求为输入1~3999范围之间的整数，将其转化为罗马数字的形式。首先问们要知道罗马数字的基本表示：
1~9: {“I”, “II”, “III”, “IV”, “V”, “VI”, “VII”, “VIII”, “IX”};
10~90: {“X”, “XX”, “XXX”, “XL”, “L”, “LX”, “LXX”, “LXXX”, “XC”};
100~900: {“C”, “CC”, “CCC”, “CD”, “D”, “DC”, “DCC”, “DCCC”,
“CM”};
1000~3000: {“M”, “MM”, “MMM”}。
如上所示罗马数字的表示都有一定规律，即每一个数字位都有不同字母按照特定的方式表答，所以我们可以将我们输入的数字从最高位依次减去罗马符号所代表的数值，比如每位数字1~3有规律，4和5较特殊，6~8有规律，9较特殊。随意将每一位分成1，4，5，9四个单位值即可。

#include <stdlib.h>#include <iostream>#include <string.h>#include <stdio.h>using namespace std;class Solution {public:    string intToRoman(int num) {        string solution;            string roman[]={"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};  //将罗马字符与数字对应         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];  //将输入的数字减去罗马字符代表的最大的数值                 solution+=roman[i]; //将减去的数值代表的罗马符号加入字符串             }          }          return solution;      }};int main(){    Solution solu;    int number;    cin>>number;    string s=solu.intToRoman(number);    cout<<s<<endl;}

运行结果展示