阿Q的博客

[38] Count and Say

https://leetcode.com/problems/count-and-say/description/

algorithms
Easy (38.05%)
Source Code: 38.count-and-say.py
Total Accepted: 229.6K
Total Submissions: 601.5K
Testcase Example: '1'

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

```
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 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"

python

class Solution(object):
    def countAndSay(self, n):
        """
        :type n: int
        :rtype: str
        """
        current = '1'
        for i in range(1, n):
            cnt = 0
            newstr = ''
            for idx, item in enumerate(current):
                if idx == 0:
                    cnt = 1
                    continue

                if current[idx] == current[idx-1]:
                    cnt += 1
                else:
                    newstr += str(cnt) + current[idx-1]
                    cnt = 1

            newstr += str(cnt) + current[-1]
            current = newstr
        return current
#
#
# s = Solution()
# for i in range(1, 6):
#     print s.countAndSay(i)