问题

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.

Notice

The sequence of integers will be represented as a string.

解法

这题思路很简单，使用两个变量：count、item一个用来计数，一个用来存储当前统计的字符。初始值在循环外设定好为'1'即可。

代码

class Solution:    # @param {int} n the nth    # @return {string} the nth sequence    def countAndSay(self, n):        # Write your code here        result = '1'        for i in xrange(1, n):            numList = list(result)            item = numList[0]            count = 0            result = ''            for ch in numList:                if ch == item:                    count += 1                else:                    result = result + str(count) + item                    item = ch                    count = 1            result = result + str(count) + item        return result