Roman to Integer Solutions in C++

// Source : https://oj.leetcode.com/problems/roman-to-integer/
// Author : Hao Chen
// Date   : 2014-07-17



#include <iostream>
#include <string>
using namespace std;

int romanCharToInt(char ch){
    int d = 0;
    switch(ch){
        case 'I':  
            d = 1;  
            break;  
        case 'V':  
            d = 5;  
            break;  
        case 'X':  
            d = 10;  
            break;  
        case 'L':  
            d = 50;  
            break;  
        case 'C':  
            d = 100;  
            break;  
        case 'D':  
            d = 500;  
            break;  
        case 'M':  
            d = 1000;  
            break;  
    }
    return d;
}
int romanToInt(string s) {
    if (s.size()<=0) return 0;
    int result = romanCharToInt(s[0]);
    for (int i=1; i<s.size(); i++){
        int prev = romanCharToInt(s[i-1]);
        int curr = romanCharToInt(s[i]);
        //if left<right such as : IV(4), XL(40), IX(9) ...
        if (prev < curr) {
            result = result - prev + (curr-prev);
        }else{
            result += curr;
        }
    }
    return result;
}

int main(int argc, char**argv)
{
    string s("XL");
    if (argc>1){
        s = argv[1];
    }
    cout << s << " : " << romanToInt(s) << endl;
    return 0;
}

#include <string>
using std::string;

class Solution {
public:
    int romanToInt(string s) {
        int res = 0;
        for (auto iter = s.rbegin(); iter != s.rend(); ++iter)
            switch (*iter)
            {
                case 'I': res += res >= 5 ? -1 : 1; break;
                case 'V': res += 5; break;
                case 'X': res += 10 * (res >= 50 ? -1 : 1); break;
                case 'L': res += 50; break;
                case 'C': res += 100 * (res >= 500 ? -1 : 1); break;
                case 'D': res += 500; break;
                case 'M': res += 1000; break;
            }
        return res;
    }
};

/// Source : https://leetcode.com/problems/roman-to-integer/description/
/// Author : liuyubobobo
/// Time   : 2018-09-17

#include <iostream>
#include <unordered_map>

using namespace std;


/// Ad-Hoc
/// Time Complexity: O(n)
/// Space Complexity: O(1)
class Solution {
public:
    int romanToInt(string s) {

        unordered_map<char, int> map = {
                {'I', 1}, {'V', 5}, {'X', 10}, {'L', 50}, {'C', 100}, {'D', 500}, {'M', 1000}};

        int res = 0;
        for(int i = 0; i < s.size(); i ++)
            if(i + 1 < s.size() && map[s[i]] < map[s[i + 1]]){
                res += map[s[i + 1]] - map[s[i]];
                i ++;
            }
            else
                res += map[s[i]];

        return res;
    }
};


int main() {

    return 0;
}