Leetcode||38. Count and Say

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

1.     12.     113.     214.     12115.     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 term of the count-and-say sequence.

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

Example 1:

Input: 1Output: "1"

Example 2:

Input: 4Output: "1211"

这题，我光理解题意就花了点时间，说好的easy呢

以3->4为例

3：21则4为一个2，一个1，所以是1211

由于数据量只到18，所以是递归解决

class Solution(object):    def countAndSay(self, n):        """        :type n: int        :rtype: str        """        res = '1'        while n > 1:        res = self.countStr(res)        n -= 1        return res    def countStr(self, s):    count = 0    res = ""    tmp = s[0]    for i in range(len(s)):    if s[i] == tmp:    count += 1    else:    res += str(count) + tmp    tmp = s[i]    count = 1    res += str(count) + tmp    return res