leetcode-count and say

The count-and-say sequence is the sequence of integers beginning as follows:
1, 11, 21, 1211, 111221, ...

1 is read off as "one 1" or 11.
11 is read off as "two 1s" or 21.
21 is read off as "one 2, then one 1" or 1211.

Given an integer n, generate the nth sequence.

Note: The sequence of integers will be represented as a string.

public class Solution {
    public String countAndSay(int n) {
        
        
        if(n==0)return new String();
        String sToCount="1";
        if(n==1)return sToCount;
        for(int i=2;i<=n;i++){
            StringBuffer sToSay=new StringBuffer();
            int len = sToCount.length();
            for(int j=0;j<len;j++){
                char start=sToCount.charAt(j);
                int num=1;
                int k=j+1;
                while(k<len&&sToCount.charAt(k)==start){
                    num++;
                    k++;
                }
                //generate the count and say
                sToSay.append(num);
                sToSay.append(sToCount.charAt(j));
                j=k-1;
            }
            sToCount=sToSay.toString();
        }
        return sToCount;
    }
}

一些注意的问题;

第一点就是，开始的==又写成等于号了。

然后就是注意在一个循环里面的循环，如果是循环的同一个量的时候，一定要注意这个变量的范围。！！！

不但要注意我们想要的条件。