Method romanToInt

Leetcode/C++/RomanToInt.cpp:59–118

{
public:
    int romanToInt(string str) 
    {
        ios_base::sync_with_stdio(false);
        cin.tie(nullptr);
        cout.tie(nullptr);
        
        int ret= 0;
        int n= str.size();
        for (int i=n-1; i>=0; i--)
        {
            switch (str[i])
            {
                case 'I':
                    if (i+1<n and (str[i+1]=='V' or str[i+1]=='X'))
                    {
                        ret-= 1;
                        break;
                    }
                    ret+= 1;
                    break;
                
                case 'V':
                    ret+= 5;
                    break;
                
                case 'X':
                    if (i+1<n and (str[i+1]=='L' or str[i+1]=='C'))
                    {
                        ret-= 10;
                        break;
                    }
                    ret+= 10;
                    break;
                
                case 'L':
                    ret+= 50;
                    break;
                
                case 'C':
                    if (i+1<n and (str[i+1]=='D' or str[i+1]=='M'))
                    {
                        ret-= 100;
                        break;

                    }
                    ret+= 100;
                    break;
                
                case 'D':
                    ret+= 500;
                    break;
                
                case 'M':
                    ret+= 1000;
                    break;         
            }
        }