leetcode笔记：Integer to Roman

一.题目描述

Given a roman numeral, convert it to an integer.

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

二.题目分析

罗马数字总结：

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”}.

关于罗马数制可参考：http://baike.baidu.com/view/1246899.htm

这个问题就是输入个阿拉伯数字，将其转换为罗马数字字符串。

该题可使用最简单的操作，即取数字的低位到高位进行操作。每次取一位，取完一位则数字除10，取出的那一位数字则用罗马数字表示出来。需要注意的是如果当前位不是原数字的各位则需要扩大10倍或者100倍等。

三.示例代码

class Solution {
public:
    string intToRoman(int num) {
        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;
    }
};

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