题目大意

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.

解题思路

刚开始题意没理解，题意是n=1时输出字符串1；n=2时，数上次字符串中的数值个数，因为上次字符串有1个1，所以输出11；n=3时，由于上次字符是11，有2个1，所以输出21；n=4时，由于上次字符串是21，有1个2和1个1，所以输出1211。

代码

class Solution(object):

    def count(self,s):
        result = '' 
        count = 0
        char = '#'
        for i in s:
            if i!=char:
                if char!='#':
                    result+=str(count)+char
                char = i
                count = 1
            else:
                count+=1
        result += str(count)+char
        return result

    def countAndSay(self, n):
        """ :type n: int :rtype: str """
        s='1'
        for i in range(1, n):
            s=self.count(s)
        return s

总结