leetcode:Roman to Integer

最新推荐文章于 2021-05-03 06:51:12 发布

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本文介绍了一种将罗马数字转换为整数的算法实现。输入范围限制在1到3999之间，通过解析每个罗马字符对应的数值，并考虑特殊组合如IV（4）和IX（9），最终得到整数结果。

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Given a roman numeral, convert it to an integer.

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

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class Solution {
    
    int getNum(char c)
    {
        if (c == 'M')
            return 1000;
        if (c == 'D')
            return 500;
        if (c == 'C')
            return 100;
        if (c == 'L')
            return 50;
        if (c == 'X')
            return 10;
        if (c == 'V')
            return 5;
        if (c == 'I')
            return 1;
    }
    
public:
    int romanToInt(string s) {
        
        int total = 0;
        int curNum = 0;
        int preNum = 0;
        int count = 0;
        
        for (int i=0; i<s.size(); i++)
        {
            curNum = getNum(s[i]);
            
            if (curNum == preNum)
            {
                count++;
                total += curNum;
            }
            else
            {
                if (preNum != 0 && curNum > preNum)
                {
                    total = total-2*preNum*count;
                }

                total += curNum;

                preNum = curNum;
                count = 1;
            }
        }
        
        return total;
        
    }
};