13. Roman to Integer

Description

Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.

Solution

和12. Integer to Roman相反，给定一个罗马数字，求对应的阿拉伯数值，注意9、4的情况

int romanToInt(string s) {
    int ret = 0;
    map<char, int> myMap = {{'M', 1000}, {'D', 500}, {'C', 100}, {'L', 50}, {'X', 10}, {'V', 5}, {'I', 1}};
    for (int i = 0; i< s.length(); ++i) {
        if (i < s.length() - 1 && myMap[s[i]] < myMap[s[i + 1]]) {
            ret += myMap[s[i + 1]] - myMap[s[i]]; //出现9、4的case
            i++;
        } else {
            ret += myMap[s[i]];
        }
    }
    return ret;
}