CountAndSay.py

'''
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.

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"
'''

class Solution:
    def countAndSay(self, n: int) -> str:
        s = "1"
        for i in range(n - 1):
            temp = s + "x" 
            c = 1
            s = ""
            for j in range(len(temp) - 1):
                if temp[j] == temp[j + 1]:
                    c += 1
                else:
                    s += str(c) + temp[j]
                    c = 1
        return s