[C++]配合枚举类型，将罗马字符串转化成数字-优快云博客

本文介绍了一种将罗马数字转换为整数的方法。通过解析罗马数字的构成规则，利用C++实现了一个简单的转换器。文章提供了完整的代码示例，并解释了特殊情况下的处理逻辑。

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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.

 1 enum {//罗马对应的数字
 2     I=1,
 3     V=5,
 4     X=10,
 5     L=50,
 6     C=100,
 7     D=500,
 8     M=1000
 9 };
10 class Solution {
11 public:
12     int romanToInt(string s) {
13         int get(char);
14         int sum=0;
15         for(int i=0;i<s.size();++i)
16         {
17             int a=get(s[i]),b=get(s[i+1]);
18             if(a>=b) sum+=a;
19             else {sum+=(b-a);++i;}
20         }
21             return sum;
22     
23     }
24 };
25 int get(char ch)//将字符串转换成数字
26 {
27     int m;
28     switch(ch)
29     {
30         case 'I':m=I;break;
31         case 'V':m=V;break;
32         case 'X':m=X;break;
33         case 'L':m=L;break;
34         case 'C':m=C;break;
35         case 'D':m=D;break;
36         case 'M':m=M;break;
37     }
38     return m;
39 }