public int romanToInt(String s) {

final int n = s.length();

final char[] w = s.toCharArray();

final int[] map = new int[26];

map['I' - 'A'] = 1;

map['V' - 'A'] = 5;

map['X' - 'A'] = 10;

map['L' - 'A'] = 50;

map['C' - 'A'] = 100;

map['D' - 'A'] = 500;

map['M' - 'A'] = 1000;

int res = 0;

for (int i = 0; i < n; i++) {

if (i == n - 1 || map[w[i + 1] - 'A'] <= map[w[i] - 'A']) {

res += map[w[i] - 'A'];

} else {

res -= map[w[i] - 'A'];

}

}

return res;

}