The function takes roman numerals and returns the sum. Program seems to struggle on inputs containing only “I”.

int romanToInt(char* s){
    long long int values[256];
    int digit[256];
    values['M'] = 1000;
    values['D'] = 500;
    values['C'] = 100;
    values['L'] = 50;
    values['X'] = 10;
    values['V'] = 5;
    values['I'] = 1;
    long long int total = 0;
    int i = 0;
    for(int j = 0; j < strlen(s); j++){
        char numeral = s[j];
        digit[j] = values[numeral];
    }
    
    while(i < strlen(s){
        if(digit[i] < digit[i + 1]){
            total = total + (digit[i + 1] - digit[i]);
            i += 2;
        }
        else{
            total = total + digit[i];
            i++;
        }
    }
    return total;
}

I changed the while loop from

while(digit[i] != 0)

to

while(i < strlen(s))

which worked to improve a number of test cases but I am not exactly sure why. From what I have been able to gather, the initial if statement is true for values containing only “I”. For example, “CCC” correctly returns 300 but “III” returns 51.