13.txt

class Solution {
    public int romanToInt(String s) {
        int arabic = 0;
        char[] roman = s.toCharArray(); 
        for (int i = 0; i <= roman.length - 1; i++) {
            if (roman[i] == 'V') {
                arabic += 5;
            }
            else if (roman[i] == 'L') {
                arabic += 50;
            }
            else if (roman[i] == 'D') {
                arabic += 500;
            }
            else if (roman[i] == 'M') {
                arabic += 1000;
            }
            else if (roman[i] == 'I') {
                if(i != roman.length - 1) {
                    if (roman[i] == 'I' && roman[i+1] == 'V') {
                        arabic += 4;
                        i++;
                    } 
                    else if (roman[i] == 'I' && roman[i+1] == 'X') {
                        arabic +=9;
                        i++;
                    }
                    else {
                        arabic += 1;
                    }
                }
                else {
                    arabic += 1;
                }
            }
            else if (roman[i] == 'X') {
                if(i != roman.length - 1) {
                    if (roman[i] == 'X' && roman[i+1] == 'L') {
                        arabic += 40;
                        i++;
                    } 
                    else if (roman[i] == 'X' && roman[i+1] == 'C') {
                        arabic +=90;
                        i++;
                    }
                    else {
                        arabic += 10;
                    }
                }
                else {
                    arabic += 10;
                }
            }  
            else if (roman[i] == 'C') {
                if(i != roman.length - 1) {
                    if (roman[i] == 'C' && roman[i+1] == 'D') {
                        arabic += 400;
                        i++;
                    } 
                    else if (roman[i] == 'C' && roman[i+1] == 'M') {
                        arabic +=900;
                        i++;
                    }
                    else {
                        arabic += 100;
                    }
                }
                else {
                    arabic += 100;
                }
            }
        }
        return arabic;
    }
}