13. 罗马数字转整数

class Solution:
    def romanToInt(self, s: str) -> int:
        nums = {
            'M': 1000,
            'CM': 900,
            'D': 500,
            'CD': 400,
            'C': 100,
            'XC': 90,
            'L': 50,
            'XL': 40,
            'X': 10,
            'IX': 9,
            'V': 5,
            'IV': 4,
            'I': 1
        }
        i = res = 0
        while i < len(s):
            if i + 1 < len(s) and s[i:i + 2] in nums:
                res += nums[s[i: i + 2]]
                i += 2
            else:
                res += nums[s[i: i + 1]]
                i += 1
        return res

class Solution {
    public int romanToInt(String s) {
        Map<String, Integer> nums = new HashMap<>();
        nums.put("M", 1000);
        nums.put("CM", 900);
        nums.put("D", 500);
        nums.put("CD", 400);
        nums.put("C", 100);
        nums.put("XC", 90);
        nums.put("L", 50);
        nums.put("XL", 40);
        nums.put("X", 10);
        nums.put("IX", 9);
        nums.put("V", 5);
        nums.put("IV", 4);
        nums.put("I", 1);
        int res = 0;
        for (int i = 0; i < s.length();) {
            if (i + 1 < s.length() && nums.get(s.substring(i, i + 2)) != null) {
                res += nums.get(s.substring(i, i + 2));
                i += 2;
            } else {
                res += nums.get(s.substring(i, i + 1));
                i += 1;
            }
        }
        return res;
    }
}

class Solution {
   public:
    int romanToInt(string s) {
        unordered_map<char, int> nums{
            {'I', 1},
            {'V', 5},
            {'X', 10},
            {'L', 50},
            {'C', 100},
            {'D', 500},
            {'M', 1000},
        };
        int ans = 0;
        for (int i = 0; i < s.size() - 1; ++i) {
            if (nums[s[i]] < nums[s[i + 1]])
                ans -= nums[s[i]];
            else
                ans += nums[s[i]];
        }
        return ans + nums[s.back()];
    }
};