Package g1501_1600.s1545_find_kth_bit_in_nth_binary_string

Class Solution

java.lang.Object
g1501_1600.s1545_find_kth_bit_in_nth_binary_string.Solution
public class Solution extends java.lang.Object
1545 - Find Kth Bit in Nth Binary String.

Medium

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 four strings in the above sequence are:

  • S1 = “0”
  • S2 = “011”
  • S3 = “0111001”
  • S4 = “011100110110001”

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 “0111001”. The 1st bit is “0”.

Example 2:

Input: n = 4, k = 11

Output: “1”

Explanation: S4 is “011100110110001”. The 11th bit is “1”.

Constraints:

  • 1 <= n <= 20
  • 1 <= k <= 2n - 1

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    char
    findKthBit(int n, int k)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • findKthBit

      public char findKthBit(int n, int k)