Leetcode - String - Roman to Integer/Integer to Roman

JerkWisdom

于 2014-08-13 15:37:03 发布

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分类专栏： Leetcode

本文链接：https://blog.youkuaiyun.com/jonathan321/article/details/38537747

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本文介绍了两个关于罗马数字与整数互相转换的算法实现。第一个算法将罗马数字转换为整数，考虑到特殊组合如IV表示4的情况。第二个算法则实现了整数到罗马数字的转换，适用于1到3999之间的数值。

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1、Roman to Integer

Given a roman numeral, convert it to an integer.

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

class Solution {
public:
    int romanToInt(string s) {
        if(s.size()==0)
            return 0;
        map<char,int> romanMap{{'M',1000},{'D',500},{'C',100},{'L',50},{'X',10},{'V',5},{'I',1}};
        auto beg=s.begin();
        int result=0;
        char prev=*beg++;;
        while(beg!=s.end())
        {
            if(romanMap[prev]<romanMap[*beg])
                result=result-romanMap[prev];
            else
                result+=romanMap[prev];
            prev=*beg++;
        }
        return result+romanMap[prev];
    }
};

2、Integer to Roman

Given an integer, convert it to a roman numeral.

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

class Solution {
public:
    string intToRoman(int num) {
        string thos[] = {"","M","MM","MMM"};
        string huns[] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};  
        string tens[] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};  
        string ones[] = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};  
        string roman;
        roman+=thos[num/1000];
        num%=1000;
        roman+=huns[num/100];
        num%=100;
        roman+=tens[num/10];
        num%=10;
        roman+=ones[num];
        return roman;
    }
};