1545.-find-kth-bit-in-nth-binary-string.md

1545. Find Kth Bit in Nth Binary String

class Solution:
    def findKthBit(self, n: int, k: int) -> str:
        rdit = {}
        idit = {}
        res = self.dfs(n)
        return res[k-1]
        
    def dfs(self, idx):
        
        if idx == 1:
            return "0"
        return self.dfs(idx - 1) + "1" + self.invert(self.dfs(idx - 1))[::-1]
    
    
    def invert(self,s):
        # print(s,"s")
        s = s.replace("1","2")
        s = s.replace("0","1")
        s = s.replace("2","0")
        # print(s,"S")
        return s