LeetCode 1545 - Find Kth Bit in Nth Binary String

class Solution:
    def findKthBit(self, n: int, k: int) -> str:
        dp = ["0"]

        def rev(val):
            return val[::-1]


        def inv(val):
            res = ""
            for i in val:
                if i == "1":
                    res +="0"
                elif i == "0":
                    res += "1"
            return res

        for i in range(n-1):
            s = dp[-1] + "1"
            s += rev(inv(dp[-1]))
            dp.append(s)
            #print(dp)
        return dp[n-1][k-1]