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程式語言 - LeetCode - C++ - 1415. The k-th Lexicographical String of All Happy Strings of Length n

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參考資訊：
https://algo.monster/liteproblems/1415

題目：


解答：

class Solution {
public:
    string getHappyString(int n, int k) {
        string tmp;
        vector<string> out;

        auto gen = [&](this auto&& gen) -> int {
            if (tmp.size() >= n) {
                out.emplace_back(tmp);
                return 1;
            }

            for (char ch = 'a'; ch <= 'c'; ++ch) {
                if (tmp.empty() || tmp.back() != ch) {
                    tmp.push_back(ch);
                    gen();
                    tmp.pop_back();
                }
            }
            return 0;
        };

        gen();
        return out.size() < k ? "" : out[k - 1];
    }
};