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# Roman to Integer（罗马数到整型数）

## 原文

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

public class Solution
{
public int RomanToInt(string s)
{
int result = 0;
Type R = typeof(Roman);
string first, second;
if (s.Length > 1)
{
first = s.Substring(0, 1); second = s.Substring(0, 2);
}
else
{
first = s.Substring(0, 1); second = "";
}
foreach (var r in Enum.GetNames(R).Reverse())
{
while ((r.Length == 1 && first == r) || (r.Length == 2 && second == r))
{
result += int.Parse(Enum.Format(R, Enum.Parse(R, r), "d"));
int lenR = r.Length, lenS = s.Length;
if (lenS - lenR < 1)
s = "";
else
s = s.Substring(lenR, lenS - lenR);

if (s.Length > 1)
{
first = s.Substring(0, 1); second = s.Substring(0, 2);
}
else if (s.Length == 1)
{
first = s.Substring(0, 1); second = "";
}
else
{
first = ""; second = "";
}
}
}
return result;
}

}

public enum Roman
{
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
};

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