solve.cpp

#include <unordered_map>
#include <string>
#include <iostream>
using namespace std;
class Solution {
	public:
		int romanToInt(string s) {
			int pre = ROMAN_TABLE[s[0]];
			int sum = pre;
			for (int i = 1; i < s.size(); ++i) {
				int cur = ROMAN_TABLE[s[i]];
				sum += cur;
				if (cur > pre) {
					sum -= 2 * pre; // 原来是＋，需要转化为－，因此减去两倍
				}
				pre = cur;
			}
			return sum;
		}
	private:
		unordered_map<char, int> ROMAN_TABLE = {
			{'I', 1},
			{'V', 5},
			{'X', 10},
			{'L', 50},
			{'C', 100},
			{'D', 500},
			{'M', 1000}
		};
};
int main(int argc, char **argv)
{
	Solution solution;
	string s;
	while (cin >> s) {
		cout << solution.romanToInt(s) << endl;
	}
	return 0;
}