13.Roman to Integer

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1、wiki：Roman数字介绍
https://en.wikipedia.org/wiki/Roman_numerals

2、

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

3、

Combination Value IV 4 IX 9 XL 40 XC 90 CD 400 CM 900

4、代码

#include <iostream>#include <string>using namespace std;class Solution {public:    int romanToInt(string s)     {        if(s.length() < 1) return 0;        int pre = 0;        int cur = 0;        int result = getNumValue(s[0]);        for(int i = 1; i < s.length(); ++i)        {            pre = getNumValue(s[i-1]);            cur = getNumValue(s[i]);            if(cur <= pre)                result += cur;            else                result = cur - 2*pre + result;        }        return result;    }    int getNumValue(char c)    {        switch (c)        {            case 'I': return 1;            case 'V': return 5;            case 'X': return 10;            case 'L': return 50;            case 'C': return 100;            case 'D': return 500;            case 'M': return 1000;            default: return 0;        }    }};int main(){   Solution s;   cout << "DCXXI: " << s.romanToInt("DCXXI") << endl;   cout << "MCMXCVI: " << s.romanToInt("MCMXCVI") << endl;}

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