Package g1501_1600.s1545_find_kth_bit_in_nth_binary_string

Class Solution

  • All Implemented Interfaces:
    
public final class Solution

    1545 - Find Kth Bit in Nth Binary String.

    Medium

    Given two positive integers n and k, the binary string <code>S<sub>n</sub></code> is formed as follows:

    • <code>S<sub>1</sub> = "0"</code>

    • <code>S<sub>i</sub> = S<sub>i - 1</sub> + "1" + reverse(invert(S<sub>i - 1</sub>))</code> for i &gt; 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:

    • <code>S<sub>1</sub> = "0"</code>

    • <code>S<sub>2</sub> = "011"</code>

    • <code>S<sub>3</sub> = "0111001"</code>

    • <code>S<sub>4</sub> = "011100110110001"</code>

    Return the <code>k<sup>th</sup></code> bit in <code>S<sub>n</sub></code>. It is guaranteed that k is valid for the given n.

    Example 1:

    Input: n = 3, k = 1

    Output: "0"

    Explanation: S<sub>3</sub> is "0111001". The 1<sup>st</sup> bit is "0".

    Example 2:

    Input: n = 4, k = 11

    Output: "1"

    Explanation: S<sub>4</sub> is "011100110110001". The 11<sup>th</sup> bit is "1".

    Constraints:

    • 1 &lt;= n &lt;= 20

    • <code>1 <= k <= 2<sup>n</sup> - 1</code>

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      Solution()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final Character findKthBit(Integer n, Integer k)

      • Methods inherited from class java.lang.Object

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