[C++]配合枚举类型，将罗马字符串转化成数字

C题目来源：leetcode

题目描述：

---

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

Symbol       Value
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

• I can be placed before V (5) and X (10) to make 4 and 9. 
• X can be placed before L (50) and C (100) to make 40 and 90. 
• C can be placed before D (500) and M (1000) to make 400 and 900.

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

---

enum {//罗马对应的数字
    I=1,
    V=5,
    X=10,
    L=50,
    C=100,
    D=500,
    M=1000
};
class Solution {
public:
    int romanToInt(string s) {
        int get(char);
        int sum=0;
        for(int i=0;i<s.size();++i)
        {
            int a=get(s[i]),b=get(s[i+1]);
            if(a>=b) sum+=a;
            else {sum+=(b-a);++i;}
        }
            return sum;
    
    }
};
int get(char ch)//将字符串转换成数字
{
    int m;
    switch(ch)
    {
        case 'I':m=I;break;
        case 'V':m=V;break;
        case 'X':m=X;break;
        case 'L':m=L;break;
        case 'C':m=C;break;
        case 'D':m=D;break;
        case 'M':m=M;break;
    }
    return m;
}

 其实枚举在这里就是一个替代功能，直接用数字也行。

17:01:56 2018-09-05@jm_epiphany