Solution.cpp

class Solution {
public:
    string smallestBeautifulString(string s, int k) {
        int n = s.size();
        for (int i = n - 1; i >= 0; --i) {
            int p = s[i] - 'a' + 1;
            for (int j = p; j < k; ++j) {
                char c = (char) ('a' + j);
                if ((i > 0 && s[i - 1] == c) || (i > 1 && s[i - 2] == c)) {
                    continue;
                }
                s[i] = c;
                for (int l = i + 1; l < n; ++l) {
                    for (int m = 0; m < k; ++m) {
                        c = (char) ('a' + m);
                        if ((l > 0 && s[l - 1] == c) || (l > 1 && s[l - 2] == c)) {
                            continue;
                        }
                        s[l] = c;
                        break;
                    }
                }
                return s;
            }
        }
        return "";
    }
};