LeetCode Problem : Roman to Integer

Problem

Given a roman numeral, convert it to an integer.

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

Code

struct romanNode
{
    char one;
    char five;
    char ten;
    romanNode* next;
    romanNode(char o,char f,char t):one(o),five(f),ten(t),next(0){}
};

class Solution {
    public:
    int rtoi(const string& s,int i,int n,int sum,romanNode* node)
    {
        if(i == n && node == 0)
            return sum;
        if(i == n)
            return rtoi(s,i,n,sum*10,node->next);
        char one = node->one;char five = node->five;char ten = node->ten;
        if(s[i] != one && s[i] != five && s[i] != ten)
            return rtoi(s,i,n,sum*10,node->next);
        int j = i;
        while(j < n && (s[j] == one || s[j] == five || s[j] == ten))
            ++j;
        int num = 0;
        int diff = j - i;
        if(diff == 1){
            if(s[i] == one)
                num = 1;
            else
                num = 5;
        }
        else if(diff == 2){
            if(s[i] == five)
                num = 6;
            else if(s[i + 1] == one)
                num = 2;
            else if(s[i + 1] == five)
                num = 4;
            else
                num = 9;
        }
        else if(diff == 3){
            if(s[i] == one)
                num = 3;
            else
                num = 7;
        }
        else
            num = 8;
        return rtoi(s,j,n,sum*10 + num,node->next);
    }
    int romanToInt(string s) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        romanNode* node = new romanNode('M','O','O');
        node->next = new romanNode('C','D','M');
        node->next->next = new romanNode('X','L','C');
        node->next->next->next = new romanNode('I','V','X');
        int sum = 0;
        int ret = rtoi(s,0,s.size(),sum,node);
        delete node->next->next->next;delete node->next->next;
        delete node->next;delete node;
        return ret;
    }

};