count-and-say.py

class Solution(object):
    def count_and_say_recursion(self, n):
        if n == 1:
            return "1"
        else:
            prev_number = self.count_and_say_recursion(n - 1)
            result = []
            prev_symbol = None
            for symbol in prev_number:
                if symbol == prev_symbol:
                    repeat_counter += 1
                    result[-1] = str(repeat_counter) + symbol
                else:
                    repeat_counter = 1
                    result.append(str(repeat_counter) + symbol)
                prev_symbol = symbol
            return ''.join(result)

    def countAndSay(self, n):
        """
        :type n: int
        :rtype: str
        """

        return str(self.count_and_say_recursion(n))


solution = Solution()

assert solution.countAndSay(1) == "1"
assert solution.countAndSay(2) == "11"
assert solution.countAndSay(3) == "21"
assert solution.countAndSay(4) == "1211"
assert solution.countAndSay(5) == "111221"