[프로그래머스/Java] 둘만의 암호

-Code

class Solution {
    public String solution(String s, String skip, int index) {
        StringBuilder answer = new StringBuilder();
        String alpa = "abcdefghijklmnopqrstuvwxyz";
        for (char c : s.toCharArray()) {
            int n = 0;
            while (n < index) {
                int idx = (c - 'a' + 1) % 26;
                c = alpa.charAt(idx);
                if (!skip.contains(String.valueOf(c))) n++;
            }
            answer.append(c);
        }

        return answer.toString();
    }
}