题目¶
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"
题意分析:¶
本题是将数字从1开始,将当前数字转化为口语对应的数字。比如1口语是1个1,记作11;11读作2个1,记作21;21读作1个2,1个1,记作1211……
'1'是第一个数字,根据输入的数字n,计算第n个这样的数字。
解答¶
class Solution(object): def say(self, nn): """ :type nn: str :rtype: str """ i = 0 result = "" while i < len(nn): count = 1 while i+1 < len(nn) and nn[i] == nn[i+1]: count += 1 i += 1 result += str(count) result += str(nn[i]) i += 1 return result def countAndSay(self, n): """ :type n: int :rtype: str """ if n == 1: return str(1) result = str(1) for i in range(1, n): result = self.say(result) return result
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