Given a roman numeral, convert it to an integer.

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

Solution:

public class Solution {
    public int romanToInt(String s) {
        int index=0,num=0,temp=0;
        while(index<s.length()){
            char c=s.charAt(index++);
            switch(c){
                case 'I':num+=1;temp=1;break;
                case 'V':num+=temp==1?3:5;break;
                case 'X':num+=temp==1?8:10;temp=10;break;
                case 'L':num+=temp==10?30:50;break;
                case 'C':num+=temp==10?80:100;temp=100;break;
                case 'D':num+=temp==100?300:500;break;
                case 'M':num+=temp==100?800:1000;break;
            }
        }
        return num;
    }
}

C语言源代码（用时18ms）：

int romanToInt(char* s) {
    int num=0,temp=0;
    while(*s){
        switch(*s){
            case 'I':num+=1;temp=1;break;
            case 'V':num+=temp==1?3:5;break;
            case 'X':num+=temp==1?8:10;temp=10;break;
            case 'L':num+=temp==10?30:50;break;
            case 'C':num+=temp==10?80:100;temp=100;break;
            case 'D':num+=temp==100?300:500;break;
            case 'M':num+=temp==100?800:1000;break;
        }
        s++;
    }
    return num;
}

class Solution {
public:
    int romanToInt(string s) {
        int index=0,num=0,temp=0;
        while(index<s.size()){
            char c=s[index++];
            switch(c){
                case 'I':num+=1;temp=1;break;
                case 'V':num+=temp==1?3:5;break;
                case 'X':num+=temp==1?8:10;temp=10;break;
                case 'L':num+=temp==10?30:50;break;
                case 'C':num+=temp==10?80:100;temp=100;break;
                case 'D':num+=temp==100?300:500;break;
                case 'M':num+=temp==100?800:1000;break;
            }
        }
        return num;
    }
};

Python源代码（用时138ms）：

class Solution:
    # @param {string} s
    # @return {integer}
    def romanToInt(self, s):
        index=0;num=0;temp=0
        while index<len(s):
            c = s[index];index+=1
            if c=='I':num+=1;temp=1
            elif c=='V':num+=3 if temp==1 else 5
            elif c=='X':num+=8 if temp==1 else 10;temp=10
            elif c=='L':num+=30 if temp==10 else 50
            elif c=='C':num+=80 if temp==10 else 100;temp=100
            elif c=='D':num+=300 if temp==100 else 500
            elif c=='M':num+=800 if temp==100 else 1000
        return num