[LeetCode]13、Roman to Integer

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.

思路：

罗马数字转int   遍历string，如果左边大于右边，则加上右边，如果小于，则减去  用sum记录结果

public class Solution13{
    public int romanToInt(String s){
        HashMap<Character, Integer> map = new HashMap<>();
        map.put('I', 1);
        map.put('V', 5);
        map.put('X', 10);
        map.put('L', 50);
        map.put('C', 100);
        map.put('D', 500);
        map.put('M', 1000);
        int sum = 0;
        
        for(int i = 0;i < s.length();i++){
            //int value = map.get(s.charAt(i));
            if(i == s.length()-1 || map.get(s.charAt(i+1))<=map.get(s.charAt(i))){
                sum += map.get(s.charAt(i));
            }
            else {
                sum -= map.get(s.charAt(i));    
            }
        }
        return sum;
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Solution13 solution13 = new Solution13();
        System.out.println(solution13.romanToInt("XLVI"));
    }
}