不难。纸上画一下就知道规律了。

public class Solution {    public String countAndSay(int n) {        StringBuilder last = new StringBuilder();        StringBuilder current = new StringBuilder("1");        int i = 1;        while (i < n)        {            last = current;            current = new StringBuilder();            int idx = 0;            while (idx < last.length())            {                char c = last.charAt(idx);                int cnt = 1;                while (idx + 1 < last.length() && c == last.charAt(idx+1))                {                    idx++;                    cnt++;                }                idx++;                current.append(cnt);                current.append(c);            }                        i++;        }              // give out current        return current.toString();    }}