https://leetcode-cn.com/problems/count-and-say/

递归

public static String countAndSay(int n) {
    if (n == 1) {
        return "1";
    }
    char[] last = countAndSay(n - 1).toCharArray();
    StringBuilder ans = new StringBuilder();
    int times = 1;
    for (int i = 1; i < last.length; i++) {
        if (last[i - 1] == last[i]) {
            times++;
        } else {
            ans.append(times);
            ans.append(last[i - 1]);
            times = 1;
        }
    }
    ans.append(times);
    ans.append(last[last.length - 1]);
    return ans.toString();
}