LeetCode——Roman to Integer

Given a roman numeral, convert it to an integer.

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

給定一個羅馬數字，把它轉換成一個整數。

把羅馬數字字符串轉換成字符數組先，如下表，每個數字僅對應一個字符，而且字符不一樣。故可從頭開始取值進行對應。

The Roman Symbols

The Romans used a special method of showing numbers, based on the following symbols:

1 5 10 50 100 500 1000 I V X L C D M

	public int romanToInt(String s) {
		Map romans = new HashMap();
		romans.put('I', 1);
		romans.put('V', 5);
		romans.put('X', 10);
		romans.put('L', 50);
		romans.put('C', 100);
		romans.put('D', 500);
		romans.put('M', 1000);
		char[] ch = s.toCharArray();
		int num = 0, val = 0;
		for (int i = 0; i < ch.length; i++) {
			val = romans.get(ch[i]);
			if (i == ch.length - 1 || romans.get(ch[i + 1]) <= val)
				num += val;
			else
				num -= val;
		}
		return num;
	}