Roman To Interger

Given a roman numeral, convert it to an integer.

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

罗马字符的表示有I,V,X,L,C,D,M

记住前一个数字

class Solution {
public:
    int romanToInt(string s) {
        map<char,int> m;
        m['I']=1;
        m['V']=5;
        m['X']=10;
        m['L']=50;
        m['C']=100;
        m['D']=500;
        m['M']=1000;

        int cur=0;
        int total=0;

        for(int i=0;i<s.length();i++)
        {
            if(cur<m[s[i]])
            {
                total-=cur;
                cur=m[s[i]];
            }
            else if(cur==m[s[i]])
            {
                cur+=m[s[i]];
            }
            else if(cur>m[s[i]])
            {
                total+=cur;
                cur=m[s[i]];
            }
        }

        total+=cur;
        return total;
    }
};

直接取数字比较，是否当前数字比后一个小

比前一种方法更加简洁

class Solution {
public:
    int romanToInt(string s) {
        map<char,int> m;
        m['I']=1;
        m['V']=5;
        m['X']=10;
        m['L']=50;
        m['C']=100;
        m['D']=500;
        m['M']=1000;

        int cur=0;
        int total=0;

        for(int i=0;i<s.length();i++)
        {
            if(i+1<s.length() && m[s[i]]<m[s[i+1]])
            total-=m[s[i]];
            else
            total+=m[s[i]];
        }

        return total;
    }
};