The count-and-say sequence is the sequence of integers with the first five terms as following:

1. 1

2. 11

3. 21

4. 1211

5. 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 where 1 ≤ n ≤ 30, generate the nth term of the count-and-say sequence.

Note: Each term of the sequence of integers will be represented as a string.

Example 1:

Input: 1
Output: "1"

Example 2:

Input: 4
Output: "1211"

注意，这个题的题干比较难理解，大概意思是第一个数是1，然后记录前一个数的读法（读作一个一），所以第二个记录为11，那第三个就是对11的读法就是2个1，记录为21，第四个就是对21的读法，1个2和1个1，记录为1211，后面以此类推。

Solution1:

class Solution:
    def countAndSay(self, n: int) -> str:
        if n == 1:
            return "1"
        last = self.countAndSay(n-1)
        new = ""
        idx = 0
        char = last[idx]
        count = 0
        while(idx < len(last)):
            if last[idx] != char:
                new = new + str(count) + char
                char = last[idx]
                count = 1
            else:
                count += 1
            idx += 1
        new = new + str(count) + char
        return new

#38 Count and Say

原文：https://www.cnblogs.com/mrdoghead/p/11869786.html