1545. Find Kth Bit in Nth Binary String

https://leetcode.com/problems/find-kth-bit-in-nth-binary-string

Description

Given two positive integers n and k, the binary string Sn is formed as follows:

• S1 = "0"

• Si = Si-1 + "1" + reverse(invert(Si-1)) for i > 1

Where + denotes the concatenation operation, reverse(x) returns the reversed string x, and invert(x) inverts all the bits in x (0 changes to 1 and 1 changes to 0).

For example, the first 4 strings in the above sequence are:

• S1= "0"

• S2= "0**1**1"

• S3= "011**1**001"

• S4 = "0111001**1**0110001"

Return the kth bit in Sn. It is guaranteed that k is valid for the given n.

Example 1:

**Input:** n = 3, k = 1
**Output:** "0"
**Explanation:** S3 is "**0**111001". The first bit is "0".

Example 2:

**Input:** n = 4, k = 11
**Output:** "1"
**Explanation:** S4 is "0111001101**1**0001". The 11th bit is "1".

Example 3:

**Input:** n = 1, k = 1

**Output:** "0"

Example 4:

**Input:** n = 2, k = 3

**Output:** "1"

Constraints:

• 1 <= n <= 20

• 1 <= k <= 2n - 1

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