13.c

int romanToInt(char *s)
{
    int romanToInt = 0;
    for (int i = 0; i < strlen(s); i++)
    {
        switch (s[i])
        {
        case 'I':
            if (i + 1 < strlen(s))
            {
                if (s[i + 1] == 'V' || s[i + 1] == 'X')
                {
                    romanToInt -= 1;
                    break;
                }
            }
            romanToInt += 1;
            break;
        case 'V':
            romanToInt += 5;
            break;
        case 'X':
            if (i + 1 < strlen(s))
            {
                if (s[i + 1] == 'L' || s[i + 1] == 'C')
                {
                    romanToInt -= 10;
                    break;
                }
            }
            romanToInt += 10;
            break;
        case 'L':
            romanToInt += 50;
            break;
        case 'C':
            if (i + 1 < strlen(s))
            {
                if (s[i + 1] == 'D' || s[i + 1] == 'M')
                {
                    romanToInt -= 100;
                    break;
                }
            }
            romanToInt += 100;
            break;
        case 'D':
            romanToInt += 500;
            break;
        case 'M':
            romanToInt += 1000;
            break;
        default:
            break;
        }
    }
    return romanToInt;
}