[LeetCode]12. Integer to Roman（自学留存）

Given an integer, convert it to a roman numeral.

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

Personal Tips: 使用map，记录1，5，10，50，100，500，1000分别对应的罗马数字，以及其规则。代码如下：

class Solution
{
public:
	Solution()
	{
		RomanTable.insert(pair<int, char>(1, 'I'));
		RomanTable.insert(pair<int, char>(5, 'V'));
		RomanTable.insert(pair<int, char>(10, 'X'));
		RomanTable.insert(pair<int, char>(50, 'L'));
		RomanTable.insert(pair<int, char>(100, 'C'));
		RomanTable.insert(pair<int, char>(500, 'D'));
		RomanTable.insert(pair<int, char>(1000, 'M'));
	}
	string intToRoman(int num) {
		string Roman;
		int count = 1000;
		while (count>0)
		{
			Roman.append(getSingleNum(num / count, count));
			num -= (num / count)*count;
			count /= 10;
		}
		return Roman;
	}
	inline string getSingleNum(int num, int count) {
		string singleRoman;
		if (num<4) return singleRoman.append(num, RomanTable[count]);
		else if (num <= 5)
		{
			singleRoman.append(5 - num, RomanTable[count]);
			singleRoman.append(1, RomanTable[5 * count]);
		}
		else if (num<9)
		{
			singleRoman.append(1, RomanTable[5 * count]);
			singleRoman.append(num - 5, RomanTable[count]);
		}
		else if (num == 9)
		{
			singleRoman.append(1, RomanTable[count]);
			singleRoman.append(1, RomanTable[10 * count]);
		}
		return singleRoman;
	}
private:
	map<int, char> RomanTable;
};