【leetcode】13. Roman to Integer

/** * Given a roman numeral, convert it to an integer. * Input is guaranteed to be within the range from 1 to 3999. */#include <iostream>#include <string>#include <unordered_map>using namespace std;//MMMCMXCIXint romanToInt(string s) {    unordered_map<char, int> map = { { 'I', 1 }, { 'V', 5 }, { 'X', 10 }, { 'L', 50 }, { 'C', 100 }, { 'D', 500 }, {'M', 1000} };    int sum = map[s.back()];    for (int i = s.length() - 2; i >= 0; i--)    {        if (map[s[i]] < map[s[i+1]])        {            sum -= map[s[i]];        }        else        {            sum += map[s[i]];        }    }    return sum;}int main(){    cout << romanToInt(string("MMMCMXCIX"));    system("pause");    return 0;}