LeetCode & Q13-Roman to Integer-Easy

Math String

Description:

Given a roman numeral, convert it to an integer.

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

What is Roman Numeral?

my Solution:

public class Solution {
    public int romanToInt(String s) {
        int[] priority = new int[s.length()];
        for (int i = 0; i < s.length(); i++) {
            switch (s.charAt(i)) {
            case 'I':
                priority[i] = 1;
                break;
            case 'V':
                priority[i] = 5;
                break;
            case 'X':
                priority[i] = 10;
                break;
            case 'L':
                priority[i] = 50;
                break;
            case 'C':
                priority[i] = 100;
                break;
            case 'D':
                priority[i] = 500;
                break;
            case 'M':
                priority[i] = 1000;
                break;
            }
        }
        int output = 0;
        for (int i = 1; i < priority.length; i++) {
            if (priority[i] > priority[i - 1]) {
            output -= priority[i-1];
            } else {
            output += priority[i-1];
            }
        }
        output += priority[priority.length - 1];
        return output;
    }
}

稍好一点的做法：

public static int romanToInt(String s) {
	int res = 0;
	for (int i = s.length() - 1; i >= 0; i--) {
		char c = s.charAt(i);
		switch (c) {
		case 'I':
			res += (res >= 5 ? -1 : 1);
			break;
		case 'V':
			res += 5;
			break;
		case 'X':
			res += 10 * (res >= 50 ? -1 : 1);
			break;
		case 'L':
			res += 50;
			break;
		case 'C':
			res += 100 * (res >= 500 ? -1 : 1);
			break;
		case 'D':
			res += 500;
			break;
		case 'M':
			res += 1000;
			break;
		}
	}
	return res;
}