# Leetcode - Count and Say Solution

The **count-and-say** sequence is a sequence of digit strings defined by the recursive formula:

`countAndSay(1) = "1"`

`countAndSay(n)`

is the way you would "say" the digit string from`countAndSay(n-1)`

, which is then converted into a different digit string.

To determine how you "say" a digit string, split it into the **minimal** number of groups so that each group is a contiguous section all of the **same character.** Then for each group, say the number of characters, then say the character. To convert the saying into a digit string, replace the counts with a number and concatenate every saying.

For example, the saying and conversion for digit string `"3322251"`

:

Given a positive integer `n`

, return *the *`n`

^{th}* term of the count-and-say sequence*.

**Example 1:**

```
Input: n = 1
Output: "1"
Explanation: This is the base case.
```

**Example 2:**

```
Input: n = 4
Output: "1211"
Explanation:
countAndSay(1) = "1"
countAndSay(2) = say "1" = one 1 = "11"
countAndSay(3) = say "11" = two 1's = "21"
countAndSay(4) = say "21" = one 2 + one 1 = "12" + "11" = "1211"
```

**Constraints:**

`1 <= n <= 30`

## Solution in Python

```
class Solution:
def countAndSay(self, n: int) -> str:
num = "1"
for i in range(n-1):
new_num = ""
for x, y in groupby(num):
new_num += str(sum(1 for _ in y))+x
num = new_num
return num
```