1576.Replace-All-?'s-to-Avoid-Consecutive-Repeating-Characters.java

// https://leetcode.com/problems/replace-all-s-to-avoid-consecutive-repeating-characters/
// algorithms
// Easy (45.97%)
// Total Accepted: 6,873
// Total Submissions: 14,951
// beats 100.0% of java submissions


class Solution {

    private static final char QUESTION = '?';

    private static final String STR_QUESTION = "?";

    private static final char Z = 'z';

    private static final char CHAR_A = 'a';

    private static final String STR_A = "A";

    public String modifyString(String s) {
        int len = s.length();
        if (len == 1) {
            return STR_QUESTION.equals(s) ? STR_A : s;
        }
        char[] chArr = s.toCharArray();

        for (int i = 0; i < len; i++) {
            if (chArr[i] != QUESTION) {
                continue;
            }

            if (i == 0) {
                chArr[0] = chArr[1] != QUESTION ? nextCh(chArr[1]) : CHAR_A;
            } else if (i == len - 1) {
                chArr[len - 1] = nextCh(chArr[len - 2]);
            } else {
                char tmp = nextCh(chArr[i - 1]);
                chArr[i] = tmp != chArr[i + 1] ? tmp : nextCh(tmp);
            }

        }

        return new String(chArr);
    }

    private char nextCh(char ch) {
        if (ch == Z) {
            return CHAR_A;
        }

        return (char) (ch + 1);
    }
}