LeetCode.38.Count and Say

原题链接：Count and Say

题目内容：
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, 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”

---

Python

class Solution(object):
    def countAndSay(self, n):
        """
        :type n: int
        :rtype: str
        """
        s = '1'
        for _ in range(n - 1):
            s = ''.join(str(len(list(group))) + num
                        for num, group in itertools.groupby(s))
        return s  

• 有关Python的内建模块itertools，可点击查看。