38. Count and Say (python 3)

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本文介绍了一种生成计数并说序列的方法，这是一种整数序列，其中每一项都是前一项的描述。例如，序列从1开始，第二项是描述第一项的“一1”，即11；第三项是描述第二项的“两1”，即21；依此类推。文章提供了一个Python类解决方案，通过递归方式生成第n项的序列。

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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”

code

class Solution:
    def count(x):

        return output
    def countAndSay(self, n):
        """
        :type n: int
        :rtype: str
        """
        d = {}
        d[1] = str(1)
        for i in range(2, n+1):
            count = []
            index = []
            count.append(1)
            output = ''
            for j in range(1, len(d[i -1])):
                if d[i -1][j] == d[i -1][j - 1]:
                    count.append(count[j - 1] + 1)
                else:
                    count.append(1)
                    index.append(j-1)
            index.append(len(d[i -1]) - 1)
            for k in index:
                output += str(count[k])
                output += d[i -1][k]
            d[i] = output
        return d[n]

tips

                if d[i -1][j] == d[i -1][j - 1]:
                    count.append(count[j - 1] + 1)
                else:
                    count.append(1)
                    index.append(j-1)
            index.append(len(d[i -1]) - 1)
            for k in index:
                output += str(count[k])
                output += d[i -1][k]